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    Nikolai Lebedev, Syed Mahmud, Igor Griva, Anders Blom & Leonard M. Tender On the electron transfer through Geobacter sulfurreducensPilA protein 2015 Journal of Polymer Science Part B: Polymer Physics
    Vol. 53(24), 1706-1717 
    DOI  
    Abstract: Geobacter sulfurreducens pili composed of the Type IV pili structural peptide PilA have been implicated as efficient electronic conductors. Though investigated experimentally, no detailed theoretical studies have been performed to date that provide quantitative estimation of the transmission spectrum, electron transfer (ET) paths, efficiency of current generation, and other factors needed for understanding possible mechanisms of conductivity. In the present work, we calculate from first principles the possibilities of electron tunneling through 3 PilA fragments which structure was identified recently by NMR. The results indicate that positively charged amino acids, arginines and lysines form electrostatic traps in the middle of the peptide preventing ET at low bias voltages (<â?¼6 V). At higher biases the traps are filled with electrons making possible sequential electron tunneling through the central part of the protein. In addition, leucines and phenylalanines form ET loops facilitating electron stabilization within the protein and sequential ET. Our results indicate that ET through the PilA protein cannot occur by coherent ET, but suggest a sequential (incoherent) mechanism. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 1706â??1717
    Keywords: conductive pili, Geobacter sulfurreducens, electroactive biofilm, protein conductance, molecular electronics, ATK, Application
    Area: molecular electronics
    BibTeX:
    @article{Lebedev2015,
      author = {Lebedev, Nikolai and Mahmud, Syed and Griva, Igor and Blom, Anders and Tender, Leonard M.},
      title = {On the electron transfer through Geobacter sulfurreducensPilA protein},
      journal = {Journal of Polymer Science Part B: Polymer Physics},
      year = {2015},
      volume = {53},
      number = {24},
      pages = {1706--1717},
      doi = {http://dx.doi.org/10.1002/polb.23809}
    }
    
    Kaoruho Sakata, Blanka Magyari-Köpe, Suyog Gupta, Yoshio Nishi, Anders Blom & Peter Deák The effects of uniaxial and biaxial strain on the electronic structure of germanium 2016 Computational Materials Science
    Vol. 112, Part A, 263 - 268 
    DOI  
    Abstract: Abstract The effects of uniaxial and biaxial strain on the electronic structure of bulk germanium are investigated using density functional theory in conjunction with four approximations for the exchange correlation interaction: the local density approximation (LDA) and generalized gradient approximation (GGA) with on-site Hubbard corrections (LDA+U, GGA+U), the meta-GGA (MGGA), and the screened hybrid functional (HSE06). The band structure and, especially, the band gap of unstrained Ge are well reproduced by these methods. The results of LDA+U/GGA+U and MGGA show that a biaxial tensile strain above 1.5% turns Ge into a direct-gap (G-G) semiconductor, whereas the indirect G-L gap is maintained for uniaxial strain up to 3%. The HSE06 results confirm a similar trend, although the predicted critical strain is lower. The effective masses were also calculated and they were found to be in good agreement with experiments for bulk Ge. It is predicted that the masses at Gamma can be tuned to be smaller/larger by tensile/compressive strain in all directions.
    Keywords: Strained Ge, semi, strain, ATK, ATK-SE, Application
    Area: semi, materials
    BibTeX:
    @article{Sakata2016,
      author = {Kaoruho Sakata and Blanka Magyari-Köpe and Suyog Gupta and Yoshio Nishi and Anders Blom and Peter Deák},
      title = {The effects of uniaxial and biaxial strain on the electronic structure of germanium },
      journal = {Computational Materials Science },
      year = {2016},
      volume = {112, Part A},
      pages = {263 - 268},
      doi = {http://dx.doi.org/10.1016/j.commatsci.2015.10.023}
    }
    
    Mamikon Gulian, Gurgen Melkonyan & Armen Gulian Engineering room-temperature superconductors via ab-initio calculations 2015 Physics Procedia: Proceedings of the 25th International Cryogenic Engineering Conference and International Cryogenic Materials Conference 2014
    Vol. 67, 963-969 
    DOI  
    Abstract: The BCS, or bosonic model of superconductivity, as Little and Ginzburg have first argued, can bring in superconductivity at room temperatures in case of high-enough frequency of bosonic mode. It was further elucidated by Kirzhnits et al., that the condition for existence of high-temperature superconductivity is closely related with negative values of the real part of dielectric function at finite values of the reciprocal lattice vectors. In view of these findings, the task is to calculate the dielectric function for real materials. Then the poles of this function will indicate the existence of bosonic excitations which can serve as a "glue" for Cooper pairing, and if the frequency is high enough, and the dielectric matrix is simultaneously negative, this material is a good candidate for very high-Tc superconductivity. Thus, our approach is to elaborate a methodology of ab-initio calculation of the dielectric function of various materials, and then point out appropriate candidates. We used the powerful codes (TDDF with the DP package in conjunction with ABINIT) for computing dielectric responses at finite values of the wave vectors in the reciprocal lattice space. Though our report is concerned with the particular problem of superconductivity, the application range of the data processing methodology is much wider. The ability to compute dielectric function of existing and still non-existing (though being predicted!) materials will have many more repercussions not only in fundamental sciences but also in technology and industry.
    Keywords: ATK, Application, phonons, superconductivity
    Area: materials
    BibTeX:
    @article{Gulian2015,
      author = {Mamikon Gulian and Gurgen Melkonyan and Armen Gulian},
      title = {Engineering room-temperature superconductors via ab-initio calculations},
      journal = {Physics Procedia: Proceedings of the 25th International Cryogenic Engineering Conference and International Cryogenic Materials Conference 2014},
      year = {2015},
      volume = {67},
      pages = {963-969},
      doi = {http://dx.doi.org/10.1016/j.phpro.2015.06.163}
    }
    
    Yipeng An, Kedong Wang, Zhongqin Yang, Zhiyong Liu, Guangrui Jia, Zhaoyong Jiao, Tianxing Wang & Guoliang Xu Negative differential resistance and rectification effects in step-like graphene nanoribbons 2014 Organic Electronics
    Vol. 17, 262 - 269 
    DOI  
    Abstract: Step-like zigzag graphene nanoribbons (ZGNRs) with different step widths are designed, and their electronic transport properties are investigated by using the non-equilibrium Green's function method combined with the density functional theory. The results reveal that one with a small step structure can exhibit better conductive capability and interesting negative differential resistance (NDR) behavior under negative applied biases. More importantly, with the increase of step width, these step-like ZGNR nanojunctions present valuable rectification effects, and show a rule that the rectification ratio increases with increasing the step width. It is also shown that the rectification effect can be further inversed and enhanced through introducing a defect around the step. Transmission spectra, densities of states, energy barriers, transmission eigenstates, and transmission pathways are analyzed subsequently to understand the electronic transport properties of these step-like ZGNR devices, which can be used in developing nanoscale NDR devices and rectifiers.
    Keywords: Charge transport, Graphene nanoribbons, Non-equilibrium Green's function, First-principles calculation, ATK, Application
    Area: graphene, nanoribbon
    BibTeX:
    @article{An2014b,
      author = {Yipeng An and Kedong Wang and Zhongqin Yang and Zhiyong Liu and Guangrui Jia and Zhaoyong Jiao and Tianxing Wang and Guoliang Xu},
      title = {Negative differential resistance and rectification effects in step-like graphene nanoribbons },
      journal = {Organic Electronics },
      year = {2014},
      volume = {17},
      pages = {262 - 269},
      doi = {http://dx.doi.org/10.1016/j.orgel.2014.12.013}
    }
    
    S. Caliskan & S. Guner First principles study on the spin dependent electronic behavior of Co doped ZnO structures joining the Al electrodes 2014 Journal of Alloys and Compounds
    Vol. 619, 91 - 97 
    DOI  
    Abstract: Employing first principles, Co doped ZnO systems between the Al electrodes were investigated through the Density Functional Theory combined with Non Equilibrium Green's Function Formalism. Electronic transport properties of these systems, in the presence of spin property, were revealed using substitutional Co atoms in a supercell. Spin resolved electronic behavior was observed to be crucially governed by atomic configuration, defined by doping position and concentration, of the system joining the electrodes. Using this feature, one can manipulate both the electronic transport and magnetic properties of an Al-Co doped ZnO-Al device structure. A nonlinearity was exhibited in current-voltage characteristics for Co doped ZnO systems attached to the Al electrodes, which implies a Schottky-like contact at the interface. The induced magnetic moment and spin polarization in the system, yielding the spin dependent transport, were elucidated.
    Keywords: First principles; Density Functional Theory; Spin dependent behavior; Doped ZnO; Al electrodes, ATK, Application
    Area: interfaces, spin
    BibTeX:
    @article{Caliskan2014,
      author = {S. Caliskan and S. Guner},
      title = {First principles study on the spin dependent electronic behavior of Co doped ZnO structures joining the Al electrodes },
      journal = {Journal of Alloys and Compounds },
      year = {2014},
      volume = {619},
      pages = {91 - 97},
      doi = {http://dx.doi.org/10.1016/j.jallcom.2014.09.037}
    }
    
    S. Caliskan & A. Laref Spin transport properties of n-polyacene molecules (n=1-15) connected to Ni surface electrodes: Theoretical analysis 2014 Scientific Reports
    Vol. 4, 7363 
    DOI  
    Abstract: Using non-equilibrium Green function formalism in conjunction with density functional theory, we explore the spin-polarized transport characteristics of several planar n-acene molecules suspended between two semi-infinite Ni electrodes via the thiol group. We examine the spin-dependence transport on Ni-n-acenes-Ni junctions, while the number of fused benzene rings varies between 1 and 15. Intriguingly, the induced magnetic moments of small acene molecules are higher than that of longer acene rings. The augmentation of fused benzene rings affects both the magnetic and transport features, such as the transmission function and conductance owing to their coupling to the Ni surface contacts via the anchoring group. The interplay between the spin-polarized transport properties, structural configuration and molecular electronic is a fortiori essential in these attractive molecular devices. Thus, this can conduct to the engineering of the electron spin transport in atomistic and molecular junctions. These prominent molecules convincingly infer that the molecular spin valves can conduct to thriving molecular devices.
    Keywords: Magnetic devices, organic-inorganic nanostructures, ATK, application
    Area: molecular electronics, spin
    BibTeX:
    @article{Caliskan2014b,
      author = {S. Caliskan and A. Laref},
      title = {Spin transport properties of n-polyacene molecules (n=1-15) connected to Ni surface electrodes: Theoretical analysis},
      journal = {Scientific Reports},
      year = {2014},
      volume = {4},
      pages = {7363},
      doi = {http://dx.doi.org/10.1038/srep07363}
    }
    
    Oscar Cespedes, May Wheeler, Timothy Moorsom & Michel Viret Unexpected Magnetic Properties of Gas-Stabilized Platinum Nanostructures in the Tunneling Regime 2014 Nano Letters
    Vol. 15(1), 45-50 
    DOI  
    Abstract: Nanostructured materials often have properties widely different from bulk, imposed by quantum limits to a physical property of the material. This includes, for example, superparamagnetism and quantized conductance, but original properties such as magnetoresistance in nonmagnetic molecular structures may also emerge. In this Letter, we report on the atomic manipulation of platinum nanocontacts in order to induce magnetoresistance. Platinum is a paramagnetic 5d metal, but atomic chains of this material have been predicted to be magnetically ordered with a large anisotropy. Remarkably, we find that a gas flow stabilizes Pt atomic structures in a break junction experiment, where we observe extraordinary resistance changes over 30000% in a temperature range up to 77 K. Simulations indicate that this behavior may stem from a previously unknown magnetically ordered, low-energy state in platinum oxide atomic chains. This is supported by measurements in Pt/PtOx superlattices revealing the presence of a ferromagnetic moment. These properties open new paths of research for atomic scale "dirty" magnetic sensors and quantum devices.
    Keywords: Magnetoresistance, platinum oxide, nanocontact, spin-dependent tunneling, ATK, Application
    Area: molecular electronics, spin
    BibTeX:
    @article{Cespedes2014,
      author = {Oscar Cespedes and May Wheeler and Timothy Moorsom and Michel Viret},
      title = {Unexpected Magnetic Properties of Gas-Stabilized Platinum Nanostructures in the Tunneling Regime},
      journal = {Nano Letters},
      year = {2014},
      volume = {15},
      number = {1},
      pages = {45-50},
      note = {PMID: 25531537},
      doi = {http://dx.doi.org/10.1021/nl504254d}
    }
    
    C.J. Dai, X.H. Yan, Y. Xiao & Y.D. Guo Electronic and transport properties of noncollinear magnetic monatomic Mn chains: Fano resonances in the superlattice of noncollinear magnetic barriers and magnetic anisotropic bands 2014 Journal of Magnetism and Magnetic Materials
    Vol. 379, 167 - 178 
    DOI  
    Abstract: By means of the density functional theory combined with non-equilibrium Green's function method, ballistic transport properties of one-dimensional noncollinear magnetic monatomic chains were investigated using the single-atomic Mn chains as a model system. Fano resonances are found to exist in the monatomic Mn chains with spin-spiral structure. Furthermore, in the monatomic Mn chains with magnetic soliton lattice, Fano resonances are enhanced and cause the conductance splitting in the transmission spectra. The Fano resonances in the noncollinear magnetic single-atomic Mn chains are arising from the coupling of the localized d-states and the extended states of the quantum channels. By constructing a theoretical model and calculating its conductance, it is found that the phenomena of Fano resonances and the accompanying conductance splitting exist universally in the superlattice of one-dimensional noncollinear magnetic barriers, due to the interference of the incident waves and reflected waves by the interfaces between the neighboring barriers. Moreover, the band structures of the ferromagnetic and spin-spiral monatomic Mn chains exhibit a strong dependence on the spatial arrangement of the magnetic moments of Mn atoms when spin-orbit coupling is considered.
    Keywords: Noncollinear magnetism; Monatomic chains; Fano resonances; Magnetic anisotropy, ATK, Application
    Area: nanowires, spin
    BibTeX:
    @article{Dai2014,
      author = {C.J. Dai and X.H. Yan and Y. Xiao and Y.D. Guo},
      title = {Electronic and transport properties of noncollinear magnetic monatomic Mn chains: Fano resonances in the superlattice of noncollinear magnetic barriers and magnetic anisotropic bands},
      journal = {Journal of Magnetism and Magnetic Materials },
      year = {2014},
      volume = {379},
      pages = {167 - 178},
      doi = {http://dx.doi.org/10.1016/j.jmmm.2014.12.024}
    }
    
    X.Q. Deng, Z.H. Zhang & C.H. Yang Improving the bias range for spin-filtering by selecting proper electrode materials 2015 RSC Advances
    Vol. 5, 15812-15817 
    DOI  
    Abstract: Using the non-equilibrium Green's function method combined with density function theory, we investigate the spin transport for carbon chains connected to electrodes of different materials. When a carbon chain is linked to the C-H (C-H2) bonded edges of H2-ZGNR-H, the carbon chain displays a net spin polarization with a net magnetic moment of 1.367 &mu;B (-0.935 &mu;B) for the C-H (C-H2) bonded edge contacts, but the directions of the net magnetic moment are opposite, and the latter system shows a larger spin conductance. Then, we choose N-doped H2-ZGNR-H as the left electrode, and the right electrode is replaced with a single-capped carbon nanotube, armchair graphene nanoribbon (AGNR), or gold electrode. The conductance and the bias range for perfect spin-filtering of these systems shows obvious differences: the carbon nanotube (Au) system shows weaker conductance, and the AGNR system shows the largest bias range for perfect spin-filtering.
    Keywords: ATK, Application, nanoribbon
    Area: graphene, spin
    BibTeX:
    @article{Deng2015,
      author = {Deng, X. Q. and Zhang, Z. H. and Yang, C. H.},
      title = {Improving the bias range for spin-filtering by selecting proper electrode materials},
      journal = {RSC Advances},
      publisher = {The Royal Society of Chemistry},
      year = {2015},
      volume = {5},
      pages = {15812-15817},
      doi = {http://dx.doi.org/10.1039/C4RA15272G}
    }
    
    G.Y. Gao & K.L. Yao Surface half-metallicity of CrS thin films and perfect spin filtering and spin diode effects of CrS/ZnSe heterostructure 2014 Applied Physics Letters
    Vol. 105(18), 182405 
    DOI  
    Abstract: Recently, ferromagnetic zinc-blende Mn1-xCrxS thin films (above x=0.5) were fabricated experimentally on ZnSe substrate, which confirmed the previous theoretical prediction of half-metallic ferromagnetism in zinc-blende CrS. Here, we theoretically reveal that both Cr- and S-terminated (001) surfaces of the CrS thin films retain the half-metallicity. The CrS/ZnSe(001) heterogeneous junction exhibits excellent spin filtering and spin diode effects, which are explained by the calculated band structure and transmission spectra. The perfect spin transport properties indicate the potential applications of half-metallic CrS in spintronic devices. All computational results are obtained by using the density functional theory combined with nonequilibrium Green's function.
    Keywords: Fermi levels, Electrodes, Heterojunctions, II-VI semiconductors, Fermi surface, ATK, Application
    Area: interfaces, semi
    BibTeX:
    @article{Gao2014,
      author = {Gao, G. Y. and Yao, K. L.},
      title = {Surface half-metallicity of CrS thin films and perfect spin filtering and spin diode effects of CrS/ZnSe heterostructure},
      journal = {Applied Physics Letters},
      year = {2014},
      volume = {105},
      number = {18},
      pages = {182405},
      doi = {http://dx.doi.org/10.1063/1.4901173}
    }
    
    Mahdi Ghorbani-Asl, Paul D. Bristowe & Krzysztof Koziol A computational study of the quantum transport properties of a Cu-CNT composite 2015 Physical Chemistry Chemical Physics
    Vol. 17, 18273-18277 
    DOI  
    Abstract: The quantum transport properties of a Cu-CNT composite are studied using a non-equilibrium Green's function approach combined with the self-consistent-charge density-functional tight-binding method. The results show that the electrical conductance of the composite depends strongly on CNT density and alignment but more weakly on chirality. Alignment with the applied bias is preferred and the conductance of the composite increases as its mass density increases.
    Keywords: ATK, Application
    Area: nanotubes, interfaces
    BibTeX:
    @article{Ghorbani-Asl2015,
      author = {Ghorbani-Asl, Mahdi and Bristowe, Paul D. and Koziol, Krzysztof},
      title = {A computational study of the quantum transport properties of a Cu-CNT composite},
      journal = {Physical Chemistry Chemical Physics},
      publisher = {The Royal Society of Chemistry},
      year = {2015},
      volume = {17},
      pages = {18273-18277},
      doi = {http://dx.doi.org/10.1039/C5CP01470K}
    }
    
    Mohit Gupta, Nitesh Gaur, Puneet Kumar, Sangeeta Singh, Neeraj K. Jaiswal & P.N. Kondekar Tailoring the electronic properties of a Z-shaped graphene field effect transistor via B/N doping 2014 Physics Letters A
    Vol. 379(7), 710 - 718 
    DOI  
    Abstract: We performed first-principles calculations to reveal a viable way for tailoring the electronic properties of Z-shaped double gate graphene field effect transistor (Z-GFET). We used B/N impurities in channel region of Z-GFET. It is revealed that doping of channel region by B/N has a significant effect on its band gap which is directly reflected in the corresponding current-voltage characteristics. A semiconducting to metallic transition is also observed in selected configurations. For B-N co-doping (config. W), direct band gap of 1.84 eV is obtained which is 20% lower than that of pristine channel. Present results are useful for future electronic devices.
    Keywords: Graphene nanoribbon, Band structure, Density of states, I-V characteristics, Transmission spectra, ATK, Application
    Area: graphene, nanoribbon
    BibTeX:
    @article{Gupta2014,
      author = {Mohit Gupta and Nitesh Gaur and Puneet Kumar and Sangeeta Singh and Neeraj K. Jaiswal and P.N. Kondekar},
      title = {Tailoring the electronic properties of a Z-shaped graphene field effect transistor via B/N doping },
      journal = {Physics Letters A },
      year = {2014},
      volume = {379},
      number = {7},
      pages = {710 - 718},
      doi = {http://dx.doi.org/10.1016/j.physleta.2014.12.046}
    }
    
    Wei Sun Leong, Xin Luo, Yida Li, Khoong Hong Khoo, Su Ying Quek & John T.L. Thong Low Resistance Metal Contacts to MoS 2 Devices with Nickel-Etched-Graphene Electrodes 2014 ACS Nano
    Vol. 9(1), 869-877 
    DOI  
    Abstract: We report an approach to achieve low-resistance contacts to MoS2 transistors with the intrinsic performance of the MoS2 channel preserved. Through a dry transfer technique and a metalcatalyzed graphene treatment process, nickel-etched-graphene electrodes were fabricated on MoS2 that yield contact resistance as low as 200 &Omega;3 &mu;m. The substantial contact enhancement (~2 orders of magnitude), as compared to pure nickel electrodes, is attributed to the much smaller work function of nickel-graphene electrodes, together with the fact that presence of zigzag edges in the treated graphene surface enhance tunneling between nickel and graphene. To this end, the successful fabrication of a clean graphene-MoS2 interface and a low resistance nickel-graphene interface is critical for the experimentally measured low contact resistance. The potential of using graphene as an electrode interlayer demonstrated in this work paves the way toward achieving high performance next-generation transistors.
    Keywords: Transition metal dichalcogenide, molybdenum disulfide, contact resistance, graphene, field-effect transistor, heterostructure, ATK, Application
    Area: graphene, interfsemi, 2dmat
    BibTeX:
    @article{Leong2014,
      author = {Leong, Wei Sun and Luo, Xin and Li, Yida and Khoo, Khoong Hong and Quek, Su Ying and Thong, John T. L.},
      title = {Low Resistance Metal Contacts to MoS 2 Devices with Nickel-Etched-Graphene Electrodes},
      journal = {ACS Nano},
      publisher = {American Chemical Society (ACS)},
      year = {2014},
      volume = {9},
      number = {1},
      pages = {869-877},
      doi = {http://dx.doi.org/10.1021/nn506567r}
    }
    
    H.F. Li, Yue Zheng, W.J. Chen, Biao Wang & G.H. Zhang Interfacial Nb-substitution induced anomalous enhancement of polarization and conductivity in BaTiO3 ferroelectric tunnel junctions 2014 AIP Advances
    Vol. 4(12), 127148 
    DOI  
    Abstract: Using density functional theory (DFT) method combined with non-equilibrium Green's function approach, we systematically investigated the structural, ferroelectric and electronic transport properties of Pt/BaTiO3/Pt ferroelectric tunnel junctions (FTJ) with the interface atomic layers doped by charge neutral Nb Ti substitution. It is found that interfacial Nb Ti substitution will produce several anomalous effects such as the vanishing of ferroelectric critical thickness and the decrease of junction resistance against tunneling current. Consequently, the thickness of the ferroelectric thin film (FTF) in the FTJ can be reduced, and both the electroresistance effect and sensitivity to external bias of the FTJ are enhanced. Our calculations indicate that the enhancements of conductivity and ferroelectric distortion can coexist in FTJs, which should be important for applications of functional electronic devices based on FTJs.
    Keywords: Niobium, Polarization, Doping, Chemical potential, Ferroelectric materials, ATK, Application
    Area: interfaces, semi
    BibTeX:
    @article{Li2014,
      author = {Li, H. F. and Zheng, Yue and Chen, W. J. and Wang, Biao and Zhang, G. H.},
      title = {Interfacial Nb-substitution induced anomalous enhancement of polarization and conductivity in BaTiO3 ferroelectric tunnel junctions},
      journal = {AIP Advances},
      year = {2014},
      volume = {4},
      number = {12},
      pages = {127148},
      doi = {http://dx.doi.org/10.1063/1.4905059}
    }
    
    Xiaobo Li, Hui-Li Li, Haiqing Wan & Guanghui Zhou Effects of amino-nitro side groups on electron device of oligo p-phenylenevinylene molecular between ZGNR electrodes 2015 Organic Electronics
    Vol. 19, 26 - 33 
    DOI  
    Abstract: We study the electronic transport property for a molecular device of an oligo (p-phenylenevinylene) (OPV) molecule without or with different side groups between two zigzag-edged graphene nanoribbon (ZGNR) electrodes. By using ab initio calculations based on density-functional theory, the effects of negative differential resistance (NDR) and spin-rectifying in I-V characteristics are revealed and explained for the proposed molecular device. Our analysis indicates that the NDR behavior comes from the conduction orbital being suppressed under certain bias voltage, while the rectifying effect is because of the asymmetry distribution of the highest occupied molecular orbital or the lowest unoccupied molecular one as well as the corresponding coupling between the molecule and electrodes. Interestingly, the transport property of the device can be improved by introducing amino-nitro side groups to the OPV molecule. The NDR behavior can be much enhanced for molecule with amino side group, and the rectification can be improved for molecule with amino and nitro side groups, respectively. In particular, the NDR behavior of peak to valley ratio can be much enhanced and a molecular rectifier which offers rectification ratio of more than three orders of magnitude up to 2863 by adding NH2 and NO2 side groups to OPV molecule, respectively.
    Keywords: OPV molecular device, NDR and spin-rectifying effects, ab initio calculations, ATK, Application
    Area: molecular electronics
    BibTeX:
    @article{Li2015,
      author = {Xiaobo Li and Hui-Li Li and Haiqing Wan and Guanghui Zhou},
      title = {Effects of amino-nitro side groups on electron device of oligo p-phenylenevinylene molecular between ZGNR electrodes},
      journal = {Organic Electronics },
      year = {2015},
      volume = {19},
      pages = {26 - 33},
      doi = {http://dx.doi.org/10.1016/j.orgel.2015.01.006}
    }
    
    Chun-Sheng Liu, Xiangfu Wang, Xiao-Juan Ye, Xiaohong Yan & Zhi Zeng Curvature and ionization-induced reversible hydrogen storage in metalized hexagonal B36 2014 The Journal of Chemical Physics
    Vol. 141(19), 194306 
    DOI  
    Abstract: The synthesis of quasiplanar boron clusters (B36) with a central hexagonal hole provides the first experimental evidence that a single-atomic-layer borophene with hexagonal vacancies is potentially viable [Z. Piazza, H. Hu, W. Li, Y. Zhao, J. Li, and L. S. Wang, Nat. Commun.5, 3113 (2014)]. However, owing to the hexagonal holes, tunning the electronic and physical properties of B36 through chemical modifications is not fully understood. Based on (van der Waals corrected-) density functional theory, we show that Li adsorbed on B36 and B-36 clusters can serve as reversible hydrogen storage media. The present results indicate that the curvature and ionization of substrates can enhance the bond strength of Li due to the energetically favorable B 2p-Li 2p orbitals hybridization. Both the polarization mechanism and the orbital hybridization between H-s orbitals and Li-2s2p orbitals contribute to the adsorption of H2 molecules and the resulting adsorption energy lies between the physisorbed and chemisorbed states. Interestingly, the number of H2 in the hydrogen storage medium can be measured by the appearance of the negative differential resistance behavior at different bias voltage regions. Furthermore, the cluster-assembled hydrogen storage materials constructed by metalized B36 clusters do not cause a decrease in the number of adsorbed hydrogen molecules per Li. The system reported here is favorable for the reversible hydrogen adsorption/desorption at ambient conditions.
    Keywords: Boron, Adsorption, Hydrogen storage, Density functional theory, Desorption, ATK, Application
    Area: molecular electronics
    BibTeX:
    @article{Liu2014b,
      author = {Liu, Chun-Sheng and Wang, Xiangfu and Ye, Xiao-Juan and Yan, Xiaohong and Zeng, Zhi},
      title = {Curvature and ionization-induced reversible hydrogen storage in metalized hexagonal B36},
      journal = {The Journal of Chemical Physics},
      year = {2014},
      volume = {141},
      number = {19},
      pages = {194306},
      doi = {http://dx.doi.org/10.1063/1.4902062}
    }
    
    Hongmei Liu, Yuanyuan He, Jinjiang Zhang, Jianwei Zhao & Li Chen A theoretical study of asymmetric electron transport through linearly aromatic molecules 2015 Physical Chemistry Chemical Physics
    Vol. 17, 4558-4568 
    DOI  
    Abstract: Electron transport through a series of polyacene molecules connected via a [small pi]-conjugated bridge (an anthracene molecule) was investigated theoretically by using the nonequilibrium Green's function formalism combined with density functional theory. The results have shown that the asymmetric current-voltage characteristics can be achieved by tuning the position of a side [small pi]-bridge linked to the main conjugated backbone. The detailed analyses of the spatial distribution of molecular orbitals as well as the current density interpret how the location of [small pi]-bridge strongly affects the intramolecular electronic coupling. The rectification in the molecular junction arises from the localization of the molecular orbitals near the Fermi level and the asymmetric shift of molecule orbital energy levels under positive and negative bias. The rectification ratio decreases with increasing the length of the [small pi]-bridge which improves intramolecular electronic coupling between aromatic rings. Furthermore, the rectification properties of conjugated molecules are just slightly affected by the anchoring positions of thiol groups. These results demonstrated that the location and the length of [small pi]-bridge, which induce the asymmetric intramolecular coupling, play key roles in the rectification of the linearly aromatic molecules.
    Keywords: ATK, Application
    Area: molecular electronics
    BibTeX:
    @article{Liu2015,
      author = {Liu, Hongmei and He, Yuanyuan and Zhang, Jinjiang and Zhao, Jianwei and Chen, Li},
      title = {A theoretical study of asymmetric electron transport through linearly aromatic molecules},
      journal = {Physical Chemistry Chemical Physics},
      publisher = {The Royal Society of Chemistry},
      year = {2015},
      volume = {17},
      pages = {4558-4568},
      doi = {http://dx.doi.org/10.1039/C4CP03887H}
    }
    
    J. Liu, Z.H. Zhang, X.Q. Deng, Z.Q. Fan & G.P. Tang Electronic structures and transport properties of armchair graphene nanoribbons by ordered doping 2015 Organic Electronics
    Vol. 18, 135 - 142 
    DOI URL 
    Abstract: Based on the first-principles method, the electronic structures and transport properties of armchair graphene nanoribbons (AGNRs) with ordered doping of B atoms or N atoms or BN molecules are studied systematically. It shows that the AGNRs may be a metal or a semiconductor depending on B or N atom-doping positions, and the calculated atom-projected density of states (atom-PDOS) indicates that B or N impurity atoms can induce the new lowest conduction band (LCB) or the highest valence band (HVB). More interestingly, as compared with the intrinsic AGNR device, the current in the B- or N-doped AGNR device with the most energetically favorable state is extremely small, completely different from a macroscopic Si semiconductor with p-type or n-type doping, which always leads to a significant increase in current. Also shown is that the doping with BN molecules generally increases the bandgap of the AGNR regardless of the doping position, but the size of these bandgaps depends on the doping positions. The current in the BN-doped AGNR device is also decreased greatly in comparison with that for the intrinsic AGNR device.
    Keywords: Graphene nanoribbons, Orderly doping, Electronic structure, Transport properties, ATK, Application
    Area: graphene
    BibTeX:
    @article{Liu2015a,
      author = {J. Liu and Z.H. Zhang and X.Q. Deng and Z.Q. Fan and G.P. Tang},
      title = {Electronic structures and transport properties of armchair graphene nanoribbons by ordered doping},
      journal = {Organic Electronics },
      year = {2015},
      volume = {18},
      pages = {135 - 142},
      url = {http://www.sciencedirect.com/science/article/pii/S1566119915000142},
      doi = {http://dx.doi.org/10.1016/j.orgel.2015.01.013}
    }
    
    Wenjiang Liu, Shaohong Cai & Xiaoqing Deng Rectifying Performance and Negative Differential Resistance Behavior of Doping Atoms Effect in Polyphenyls 2015 Journal of Electronic Materials
    Vol. 44(2), 667-674 
    DOI  
    Abstract: The properties of two polyphenyls doped with nitrogen and boron atoms, which are connected by an alkane chain, are investigated by the non-equilibrium Green's function method combined with the density functional theory. It has been found that the doped sites have significant effects on the current-voltage characteristics. For models with the N(B) near the alkane chain, the rectification ratio is smaller, but the rectifying performance of models with the N(B) far away from the alkane chain is tremendously enhanced and rectification ratios can reach 280, alongside negative differential resistance behavior. The mechanisms for these phenomena are explained by transmission spectra, the molecular projected self-consistent Hamiltonian eigenstates, electrostatic potential distribution, and projected density of states.
    Keywords: Rectifying; negative differential resistance; doping; molecular electronics, ATK, Application
    Area: molecular electronics
    BibTeX:
    @article{Liu2015b,
      author = {Liu, Wenjiang and Cai, Shaohong and Deng, Xiaoqing},
      title = {Rectifying Performance and Negative Differential Resistance Behavior of Doping Atoms Effect in Polyphenyls},
      journal = {Journal of Electronic Materials},
      publisher = {Springer US},
      year = {2015},
      volume = {44},
      number = {2},
      pages = {667-674},
      doi = {http://dx.doi.org/10.1007/s11664-014-3563-x}
    }
    
    Jie Ma, Chuan-Lu Yang, Mei-Shan Wang & Xiao-Guang Ma Controlling the electronic transport properties of the tetrapyrimidinyl molecule with atom modified sulfur bridge 2015 RSC Advances
    Vol. 5, 10675-10679 
    DOI  
    Abstract: The effect of the modified sulfur bridge on the I-V characteristics of a two-probe system of tetrapyrimidinyl molecules and Au electrodes is explored based on density functional theory with nonequilibrium Green's function. Five modified sulfur bridges with H, N or O atoms are considered. The two-probe system demonstrates a switch behavior when the sulfur bridge is modified with the H atom, and negative differential resistance behavior when modified with N or O. The analysis for the mechanism of the various properties has been presented with the highest occupied molecular orbital, lowest unoccupied molecular orbital and the transmission spectra.
    Keywords: ATK, Application
    Area: molecular electronics
    BibTeX:
    @article{Ma2015,
      author = {Ma, Jie and Yang, Chuan-Lu and Wang, Mei-Shan and Ma, Xiao-Guang},
      title = {Controlling the electronic transport properties of the tetrapyrimidinyl molecule with atom modified sulfur bridge},
      journal = {RSC Advances},
      publisher = {The Royal Society of Chemistry},
      year = {2015},
      volume = {5},
      pages = {10675-10679},
      doi = {http://dx.doi.org/10.1039/C4RA14163F}
    }
    
    Phuong Duc Nguyen, Thanh Cong Nguyen, Faruque M. Hossain, Duc Hau Huynh, Robin Evans & Efstratios Skafidas Negative differential resistance effect in planar graphene nanoribbon break junctions 2014 Nanoscale
    Vol. 7(1), 289-293 
    DOI  
    Abstract: Graphene is an interesting material with a number of desirable electrical properties. Graphene-based negative differential resistance (NDR) devices hold great potential for enabling the implementation of several elements required in electronic circuits and systems. In this article we propose a novel device structure that exhibits NDR using single layer graphene that is able to be fabricated using standard lithography techniques. Using theoretical simulation, we show that graphene nanoribbon (GNR) junctions exhibit NDR effect if a gap is introduced in the structure in the transport direction of the ribbon. Using standard lithography techniques, we produce a GNR and use electro-migration to create a nanogap by breaking the GNR device. Scanning electron microscopy images show the formation of a tunnel gap. The predicted NDR phenomenon is experimentally verified in the current-voltage characteristic of the device. The linear and non-linear characteristics of the I-V responses before and after breakdown confirm that the NDR effect arises from the tunnel gap.
    Keywords: ATK, Application
    Area: graphene
    BibTeX:
    @article{Nguyen2014,
      author = {Nguyen, Phuong Duc and Nguyen, Thanh Cong and Hossain, Faruque M. and Huynh, Duc Hau and Evans, Robin and Skafidas, Efstratios},
      title = {Negative differential resistance effect in planar graphene nanoribbon break junctions},
      journal = {Nanoscale},
      publisher = {Royal Society of Chemistry (RSC)},
      year = {2014},
      volume = {7},
      number = {1},
      pages = {289-293},
      doi = {http://dx.doi.org/10.1039/c4nr05133e}
    }
    
    Feng Pan, Yangyang Wang, Kaili Jiang, Zeyuan Ni, Jianhua Ma, Jiaxin Zheng, Ruge Quhe, Junjie Shi, Jinbo Yang, Changle Chen & Jing Lu Silicene Nanomesh 2014 Scientific Reports
    Vol. 5, 9075 
    DOI  
    Abstract: Similar to graphene, zero band gap limits the application of silicene in nanoelectronics despite of its high carrier mobility. By using first-principles calculations, we reveal that a band gap is opened in silicene nanomesh (SNM) when the width W of the wall between the neighboring holes is even. The size of the band gap increases with the reduced W and has a simple relation with the ratio of the removed Si atom and the total Si atom numbers of silicene. Quantum transport simulation reveals that the sub-10 nm single-gated SNM field effect transistors show excellent performance at zero temperature but such a performance is greatly degraded at room temperature.
    Keywords: ATK, application, silicene
    Area: 2dmat
    BibTeX:
    @article{Pan2014a,
      author = {Feng Pan and Yangyang Wang and Kaili Jiang and Zeyuan Ni and Jianhua Ma and Jiaxin Zheng and Ruge Quhe and Junjie Shi and Jinbo Yang and Changle Chen and Jing Lu},
      title = {Silicene Nanomesh},
      journal = {Scientific Reports},
      year = {2014},
      volume = {5},
      pages = {9075},
      doi = {http://dx.doi.org/10.1038/srep09075}
    }
    
    S.J. Ray Single molecule transistor based nanopore for the detection of nicotine 2014 Journal of Applied Physics
    Vol. 116(24), 244307 
    DOI  
    Abstract: A nanopore based detection methodology was proposed and investigated for the detection of Nicotine. This technique uses a Single Molecular Transistor working as a nanopore operational in the Coulomb Blockade regime. When the Nicotine molecule is pulled through the nanopore area surrounded by the Source(S), Drain (D), and Gate electrodes, the charge stability diagram can detect the presence of the molecule and is unique for a specific molecular structure. Due to the weak coupling between the different electrodes which is set by the nanopore size, the molecular energy states stay almost unaffected by the electrostatic environment that can be realised from the charge stability diagram. Identification of different orientation and position of the Nicotine molecule within the nanopore area can be made from specific regions of overlap between different charge states on the stability diagram that could be used as an electronic fingerprint for detection. This method could be advantageous and useful to detect the presence of Nicotine in smoke which is usually performed using chemical chromatography techniques.
    Keywords: Nanoporous materials, Electrodes, Diamond, Chromatography, Dielectrics, ATK, Application
    Area: molecular electronics
    BibTeX:
    @article{Ray2014,
      author = {Ray, S. J.},
      title = {Single molecule transistor based nanopore for the detection of nicotine},
      journal = {Journal of Applied Physics},
      year = {2014},
      volume = {116},
      number = {24},
      pages = {244307},
      doi = {http://dx.doi.org/10.1063/1.4904358}
    }
    
    Jian Shao, X.Y. Zhang, Yue Zheng, Biao Wang & Yun Chen Length-dependent rectification and negative differential resistance in heterometallic n-alkanedithiol junctions 2015 RSC Advances
    Vol. 5, 13917-13922 
    DOI  
    Abstract: The transport properties of heterometallic n-alkanedithiol junctions have been investigated via first-principles calculations. Results show that the heterometallic n-alkanedithiol junctions exhibit significant rectification at lower voltage. A negative differential resistance was found at higher voltage, which increases with the increase of the n-alkanedithiol backbone length. In order to explain these phenomena, the molecular orbitals of n-alkanedithiol have been analyzed between certain electrodes. It is found that the rectification is induced by asymmetric orbital profiles between the heterometallic electrodes, and negative differential resistance arises when the molecular orbitals cross the band edge provided by the metal-sulfur bond.
    Keywords: ATK, Application
    Area: molecular electronics
    BibTeX:
    @article{Shao2015,
      author = {Shao, Jian and Zhang, X. Y. and Zheng, Yue and Wang, Biao and Chen, Yun},
      title = {Length-dependent rectification and negative differential resistance in heterometallic n-alkanedithiol junctions},
      journal = {RSC Advances},
      publisher = {The Royal Society of Chemistry},
      year = {2015},
      volume = {5},
      pages = {13917-13922},
      doi = {http://dx.doi.org/10.1039/C4RA14999H}
    }
    
    Anurag Srivastava & R. Chandiramouli Band structure and transport studies on impurity substituted InSe nanosheet - A first-principles investigation 2014 Superlattices and Microstructures
    Vol. 79, 135 - 147 
    DOI URL 
    Abstract: The band structure and electronic transport properties of InSe nanosheet with substitution impurity are studied using density functional theory. The nanostructures of InSe nanosheet exhibit metallic nature. The effect of substitution due to sulfur, tellurium and gallium influences the band structure. The density of states spectrum envisions the density of charges across the InSe nanosheet. The peak amplitudes are observed near the Fermi level and along the valence band in InSe nanosheet. The electron density provides the visualization of density of electrons across InSe nanosheet. The electron density is found to be more on selenium sites than on indium sites. The electronic transport property of InSe nanosheet molecular device is discussed in terms of transmission spectrum, an increase in transmission is observed on moving toward Fermi level along the valence band. The transmission pathways provide the visualization of transmission of electrons along InSe nanosheet. The results of the present work provide insight to tune the band structure of InSe nanosheet with substitution impurity and enhance the electronic transport property of InSe nanosheet.
    Keywords: Indium selenide, Nanosheet, Transport property, Band structure, Electron density, ATK, Application
    Area: semi
    BibTeX:
    @article{Srivastava2014,
      author = {Anurag Srivastava and R. Chandiramouli},
      title = {Band structure and transport studies on impurity substituted InSe nanosheet - A first-principles investigation},
      journal = {Superlattices and Microstructures },
      year = {2014},
      volume = {79},
      pages = {135 - 147},
      url = {http://www.sciencedirect.com/science/article/pii/S0749603614004923},
      doi = {http://dx.doi.org/10.1016/j.spmi.2014.12.024}
    }
    
    Pankaj Srivastava, Subhra Dhar & Neeraj K. Jaiswal Potential spin-polarized transport in gold-doped armchair graphene nanoribbons 2015 Physics Letters A
    Vol. 379(9), 835 - 842 
    DOI URL 
    Abstract: Based on NEGF-DFT computations, systematic investigation of electronic, magnetic and transport properties of AGNRs are done by employing Au through different doping mechanisms. Remarkable Au-AGNR bonding is observed in case of substitution due to the presence of impurity at the edges. Both substitution and adsorption of Au on AGNR surface induce significant changes in the electronic spin transport of the sp2 hybridized carbon sheets. AGNRs are semiconducting with lower total energy for the FM configuration, and the I-V characteristics reveal semiconductor to metal transition of Au-doped AGNR. The spin injection is voltage controlled in all the investigated Au-doped AGNRs.
    Keywords: Armchair graphene nanoribbon, Gold, Spin, Adsorption, Substitution, Current, ATK, Application
    Area: graphene
    BibTeX:
    @article{Srivastava2015,
      author = {Pankaj Srivastava and Subhra Dhar and Neeraj K. Jaiswal},
      title = {Potential spin-polarized transport in gold-doped armchair graphene nanoribbons },
      journal = {Physics Letters A },
      year = {2015},
      volume = {379},
      number = {9},
      pages = {835 - 842},
      url = {http://www.sciencedirect.com/science/article/pii/S0375960114012882},
      doi = {http://dx.doi.org/10.1016/j.physleta.2014.12.047}
    }
    
    Yangyang Wang, Zeyuan Ni, Qihang Liu, Ruge Quhe, Jiaxin Zheng, Meng Ye, Dapeng Yu, Junjie Shi, Jinbo Yang, Ju Li & Jing Lu All-Metallic Vertical Transistors Based on Stacked Dirac Materials 2015 Advanced Functional Materials
    Vol. 25(1), 68-77 
    DOI  
    Abstract: It is an ongoing pursuit to use metal as a channel material in a field effect transistor. All metallic transistor can be fabricated from pristine semimetallic Dirac materials (such as graphene, silicene, and germanene), but the on/off current ratio is very low. In a vertical heterostructure composed by two Dirac materials, the Dirac cones of the two materials survive the weak interlayer van der Waals interaction based on density functional theory method, and electron transport from the Dirac cone of one material to the one of the other material is therefore forbidden without assistance of phonon because of momentum mismatch. First-principles quantum transport simulations of the all-metallic vertical Dirac material heterostructure devices confirm the existence of a transport gap of over 0.4 eV, accompanied by a switching ratio of over 10^4. Such a striking behavior is robust against the relative rotation between the two Dirac materials and can be extended to twisted bilayer graphene. Therefore, all-metallic junction can be a semiconductor and novel avenue is opened up for Dirac material vertical structures in high-performance devices without opening their band gaps.
    Keywords: Dirac materials, vertical heterostructure, field effect transistor, density functional theory, quantum transport, ATK, Application
    Area: 2dmat, interfaces
    BibTeX:
    @article{Wang2015,
      author = {Wang, Yangyang and Ni, Zeyuan and Liu, Qihang and Quhe, Ruge and Zheng, Jiaxin and Ye, Meng and Yu, Dapeng and Shi, Junjie and Yang, Jinbo and Li, Ju and Lu, Jing},
      title = {All-Metallic Vertical Transistors Based on Stacked Dirac Materials},
      journal = {Advanced Functional Materials},
      year = {2015},
      volume = {25},
      number = {1},
      pages = {68-77},
      doi = {http://dx.doi.org/10.1002/adfm.201402904}
    }
    
    Qiu-Hua Wu, Peng Zhao & De-Sheng Liu Perfect Spin-Filtering in 4H-TAHDI-Based Molecular Devices: the Effect of N-Substitution 2014 Chinese Physics Letters
    Vol. 31(10), 107302 
    DOI URL 
    Abstract: Based on the non-equilibrium Green's function formalism and spin-polarized density functional theory calculations, we investigate the spin transport properties of HDI and terahydrotetraazahexacene diimide (4H-TAHDI) with two ferromagnetic zigzag-edge graphene nanoribbon electrodes. Compared with HDI, four carbon atoms in the hexacene part of 4H-TAHDI are substituted by nitrogen atoms. The results show that the nitrogen substitution can improve significantly the spin-filtering performance and 4H-TAHDI can be used as a perfect spin filter. Our study indicates that suitable chemical substitution is a possible way to realize high-efficiency spin filters.
    Keywords: ATK, Application
    Area: molecular electronics, spin
    BibTeX:
    @article{Wu2014b,
      author = {Wu, Qiu-Hua and Zhao, Peng and Liu, De-Sheng},
      title = {Perfect Spin-Filtering in 4H-TAHDI-Based Molecular Devices: the Effect of N-Substitution},
      journal = {Chinese Physics Letters},
      year = {2014},
      volume = {31},
      number = {10},
      pages = {107302},
      url = {http://stacks.iop.org/0256-307X/31/i=10/a=107302},
      doi = {http://dx.doi.org/10.1088/0256-307X/31/10/107302}
    }
    
    Qiu-Hua Wu, Peng Zhao, De-Sheng Liu, Shu-Juan Li & Gang Chen Rectifying, giant magnetoresistance, spin-filtering, newgative differential resistance, and switching effects in single-molecule magnet Mn(dmit)2-based molecular device with graphene nanoribbon electrodes 2014 Organic Electronics
    Vol. 15(12), 3615 - 3623 
    DOI  
    Abstract: By applying the density functional theory and the nonequilibrium Green's function formalism, we investigate the spin transport properties of a single-molecule magnet Mn(dmit)2 sandwiched between two ferromagnetic zigzag-edge graphene nanoribbon electrodes. The results show that the system can present large rectifying, giant magnetoresistance, spin-filtering and negative differential resistance effects with the help of magnetic field modulation. Moreover, an improved switching effect can also be realized by changing the orientation between planes of two dmit ligands. Therefore, the system will provide the possibilities for a multifunctional molecular device design.
    Keywords: Rectifying, Giant magnetoresistance, Spin-filtering, Negative differential resistance, Switching, ATK, Application
    Area: molecular electronics, spin
    BibTeX:
    @article{Wu2014e,
      author = {Qiu-Hua Wu and Peng Zhao and De-Sheng Liu and Shu-Juan Li and Gang Chen},
      title = {Rectifying, giant magnetoresistance, spin-filtering, newgative differential resistance, and switching effects in single-molecule magnet Mn(dmit)2-based molecular device with graphene nanoribbon electrodes },
      journal = {Organic Electronics},
      year = {2014},
      volume = {15},
      number = {12},
      pages = {3615 - 3623},
      doi = {http://dx.doi.org/10.1016/j.orgel.2014.10.010}
    }
    
    Zhi Yang, Donghong Wang, Xuguang Liu, Li-Chun Xu, Shijie Xiong & Bingshe Xu Magnetic and Quantum Transport Properties of Small-Sized Transition-Metal-Pentalene Sandwich Cluster 2014 The Journal of Physical Chemistry C
    Vol. 118(51), 29695-29703 
    DOI  
    Abstract: The chemical bonds and magnetic and quantum transport properties of small-sized transition-metal-pentalene sandwich clusters TM2nPnn+1 (TM = V, Cr, Mn, Co, and Ni; n = 1, 2) were investigated by using density functional theory and nonequilibrium Green's function method. Theoretical results show that TM2nPnn+1 sandwiches have high stabilities. The TM-TM bond order gradually decreases with the increase of 3d electron number of TM atoms and TM2nPnn+1 could exhibit different spin states. With Au as two electrodes, significant spin-filter capability was observed in TM2nPnn+1, and such a filter can be switched on/off by changing the spin state. In addition, giant magnetoresistance was also found in the systems. These interesting quantum transport properties indicate that TM2nPnn+1 sandwiches are promising materials for designing molecular junction with different functions.
    Keywords: ATK, Application
    Area: molecular electronics, spin
    BibTeX:
    @article{Yang2014d,
      author = {Zhi Yang and Donghong Wang and Xuguang Liu and Li-Chun Xu and Shijie Xiong and Bingshe Xu},
      title = {Magnetic and Quantum Transport Properties of Small-Sized Transition-Metal-Pentalene Sandwich Cluster},
      journal = {The Journal of Physical Chemistry C},
      year = {2014},
      volume = {118},
      number = {51},
      pages = {29695-29703},
      doi = {http://dx.doi.org/10.1021/jp511443j}
    }
    
    Xi-Feng Yang, Wen-Qian Zhou, Xue-Kun Hong, Yu-Shen Liu, Xue-Feng Wang & Jin-Fu Feng Half-metallic properties, single-spin negative differential resistance, and large single-spin Seebeck effects induced by chemical doping in zigzag-edged graphene nanoribbons 2015 The Journal of Chemical Physics
    Vol. 142(2), 024706 
    DOI  
    Abstract: Ab initio calculations combining density-functional theory and nonequilibrium Green's function are performed to investigate the effects of either single B atom or single N atom dopant in zigzag-edged graphene nanoribbons (ZGNRs) with the ferromagnetic state on the spin-dependent transport properties and thermospin performances. A spin-up (spin-down) localized state near the Fermi level can be induced by these dopants, resulting in a half-metallic property with 100% negative (positive) spin polarization at the Fermi level due to the destructive quantum interference effects. In addition, the highly spin-polarized electric current in the low bias-voltage regime and single-spin negative differential resistance in the high bias-voltage regime are also observed in these doped ZGNRs. Moreover, the large spin-up (spin-down) Seebeck coefficient and the very weak spin-down (spin-up) Seebeck effect of the B(N)-doped ZGNRs near the Fermi level are simultaneously achieved, indicating that the spin Seebeck effect is comparable to the corresponding charge Seebeck effect.
    Keywords: Doping, Fermi levels, Thermoelectric effects, Electric currents, Localized states, ATK, Application
    Area: graphene, spin, thermo
    BibTeX:
    @article{Yang2015a,
      author = {Yang, Xi-Feng and Zhou, Wen-Qian and Hong, Xue-Kun and Liu, Yu-Shen and Wang, Xue-Feng and Feng, Jin-Fu},
      title = {Half-metallic properties, single-spin negative differential resistance, and large single-spin Seebeck effects induced by chemical doping in zigzag-edged graphene nanoribbons},
      journal = {The Journal of Chemical Physics},
      year = {2015},
      volume = {142},
      number = {2},
      pages = {024706},
      doi = {http://dx.doi.org/10.1063/1.4904295}
    }
    
    A. Zahir, S.A.A. Zaidi, A. Pulimeno, M. Graziano, D. Demarchi, G. Masera & G. Piccinini Molecular transistor circuits: From device model to circuit simulation 2014 Nanoscale Architectures (NANOARCH), 2014 IEEE/ACM International Symposium on, 129-134  DOI  
    Abstract: Molecular devices have been proposed as an alternative solution for the design and fabrication of complex logic functions. In this paper a hybrid model of the molecular transistor (MT) is used to simulate different logic circuits. The model is based on the density function theory (DFT) combined with the Non Equilibrium Greens Function (NEGF) to find the transmission spectrum (TS) at equilibrium. The self-consistent method is used to calculate the I-V characteristics at nonequilibrium condition, considering the more realistic case of broadening of energy levels under the assumption of strong molecule electrode coupling. We have used a four terminal device with source, drain and two gate electrodes: one (backgate) used to increase the ION/IOFF ratio and the other as normal control gate. The very same device is contextualized in the case of a structure feasible with currently available technology and several technological parameters are used to explore the solution space. This ensemble has been described and simulated using VHDL-AMS and allowed the design of a library of logic cells e.g NAND, NOR, Inverter and Half Adder suitable for architecture design. Results are given on both the modeling level and the circuits functional performance. Our findings represent an important breakthrough in the state of the art 1) for the methodology and design flow used and 2) for the detailed understanding on the device analyzed and optimized with the point of view of the circuit designer.
    Keywords: Green's function methods;adders;circuit simulation;density functional theory;hardware description languages;logic design;logic gates;molecular electronics;transistor circuits;DFT;I-V characteristics;MT;NAND;NEGF;NOR;TS;VHDL-AMS;architecture design;circuit functional performance;circuit simulation;complex logic functions;density function theory;design flow;device model;drain electrodes;energy levels;gate electrodes;half adder;inverter;logic cells;logic circuits;modeling level;molecular transistor circuits;molecule electrode coupling;nonequilibrium Green's function;normal control gate;self-consistent method;terminal device;transmission spectrum;Electrodes;Energy states;Integrated circuit modeling;Inverters;Logic circuits;Logic gates;Transistors, ATK, Application
    Area: molecular electronics
    BibTeX:
    @inproceedings{Zahir2014,
      author = {Zahir, A. and Zaidi, S.A.A. and Pulimeno, A. and Graziano, M. and Demarchi, D. and Masera, G. and Piccinini, G.},
      title = {Molecular transistor circuits: From device model to circuit simulation},
      booktitle = {Nanoscale Architectures (NANOARCH), 2014 IEEE/ACM International Symposium on},
      year = {2014},
      pages = {129-134},
      doi = {http://dx.doi.org/10.1109/NANOARCH.2014.6880492}
    }
    
    Guiling Zhang, Sun Peng, Yan Shang, Zhao-Di Yang & Xiao Cheng Zeng Electronic and transport properties of carbon and boron-nitride ferrocene nanopeapods 2014 J. Mater. Chem. C
    Vol. 2(46), 10017-10030 
    DOI  
    Abstract: Electronic and transport properties of novel ferrocene based carbon nanotube (CNT) and boron-nitride nanotube (BNNT) nanopeapods, including Fe(Cp)2@CNT, Fe2(Cp)3@CNT, Fe(Cp)2@BNNT, and Fe2(Cp)3@BNNT (where Cp refers as cyclopentadiene), are investigated using the density functional theory and non-equilibrium Green's function methods. Computed electronic structures of the Fe(Cp)2@CNT and Fe2(Cp)3@CNT nanopeapods suggest that their electric conductivity is primarily contributed by the CNT &pi; channel while the electron hopping from the core Fe(Cp)2 or Fe2(Cp)3 to the sheath CNT may have some contribution to the transport properties. Encapsulating Fe(Cp)2 into BNNT is more favorable for the electron conduction, owing to the splitting of the BNNT bandgap by the Fe(Cp)2 state. In contrast, introducing Fe2(Cp)3 into the BNNT is not beneficial to the conduction due to intramolecular electron transfer within the core Fe2(Cp)3 which can cause a trap effect. Because the transport channels can be changed by the applied bias voltage, the transport properties cannot be solely predicted from the electronic structures of infinite systems alone. For computing transport properties, we use two-probe device model systems with a finite-sized nanopeapod sandwiched between two CNT electrodes. Again, we find that encapsulating either Fe(Cp)2 or Fe2(Cp)3 into CNTs has little effect on the conductivity owing to the strong metallic character of the CNT sheath. Encapsulating Fe(Cp)2 into BNNTs can notably enhance electron conducting due to electron hopping from the core Fe(Cp)2 to the sheath BNNT. Encapsulating Fe2(Cp)3 into BNNTs, however, has little effect on the electron conductivity of BNNT nanopeapods due to the trap effect of the longer guest molecules. Hence, the length of guest molecules can effectively tune electronic and transport properties of the BNNT nanopeapods.
    Keywords: ATK, Application
    Area: nanotubes
    BibTeX:
    @article{Zhang2014b,
      author = {Zhang, Guiling and Peng, Sun and Shang, Yan and Yang, Zhao-Di and Zeng, Xiao Cheng},
      title = {Electronic and transport properties of carbon and boron-nitride ferrocene nanopeapods},
      journal = {J. Mater. Chem. C},
      publisher = {Royal Society of Chemistry (RSC)},
      year = {2014},
      volume = {2},
      number = {46},
      pages = {10017-10030},
      doi = {http://dx.doi.org/10.1039/c4tc01906g}
    }
    
    Wen kai Zhao, Bin Cui, Chang feng Fang, Guo min Ji, Jing fen Zhao, Xiang ru Kong, Dong qing Zou, Xiao hui Jiang, Dong mei Li & De sheng Liu Rectification inversion in oxygen substituted graphyne-graphene-based heterojunctions 2014 Phys. Chem. Chem. Phys.
    Vol. 17, 3115-3122 
    DOI  
    Abstract: Current rectification is found in oxygen-substituted zigzag graphyne nanoribbon/hydrogen-terminated zigzag graphene nanoribbon heterostructure junctions, from the application of nonequilibrium Green's function formalism combined with density functional theory. This behavior could be tuned by varying the number and location of oxygen atoms in the zigzag graphyne nanoribbon parts, and the rectification direction could be reversed due to the parity limitation tunneling effect. Moreover, an obvious negative differential resistance behavior is found and may be explained by two different mechanisms.
    Keywords: ATK, Application
    Area: molecular electronics, graphene
    BibTeX:
    @article{Zhao2014e,
      author = {Zhao, Wen-kai and Cui, Bin and Fang, Chang-feng and Ji, Guo-min and Zhao, Jing-fen and Kong, Xiang-ru and Zou, Dong-qing and Jiang, Xiao-hui and Li, Dong-mei and Liu, De-sheng},
      title = {Rectification inversion in oxygen substituted graphyne-graphene-based heterojunctions},
      journal = {Phys. Chem. Chem. Phys.},
      publisher = {The Royal Society of Chemistry},
      year = {2014},
      volume = {17},
      pages = {3115-3122},
      doi = {http://dx.doi.org/10.1039/C4CP04859H}
    }
    
    Jiming Zheng, Xiaoqing Deng, Jianwei Zhao, Ping Guo, Chongfeng Guo, Zhaoyu Ren & Jintao Bai Coupling site controlled spin transport through the graphene nanoribbon junction: A first principles investigation 2015 Computational Materials Science
    Vol. 99, 203 - 208 
    DOI  
    Abstract: A new type of nano-junctions based on Zigzag graphene nanoribbons (ZGNRs) has been proposed and investigated by first-principles calculations. The results show that large spin polarization of currents would be achieved when the junctions adopted the configuration that two ZGNR leads coupled each other along one edge. By virtue of spatial separation of the two spin edge states, only one spin channel is opened in those junctions at certain energy range, and spin polarized currents will be produced under a low bias. No more efforts are required to change ZGNR from the antiferromagnetic (AFM) ground states to the ferromagnetic (FM) states. Specially, this feature is stable, by changing the width of ZGNRs, modifying the edge morphology, and varying dihedral angle between two ZGNRs, spin polarization of currents are still observed. Our findings indicate that this approach is simple and efficient for spintronics design.
    Keywords: Spintronics; Graphene nanoribbons; Coupling site control; First-principles calculation, ATK, Application
    Area: graphene
    BibTeX:
    @article{Zheng2015,
      author = {Jiming Zheng and Xiaoqing Deng and Jianwei Zhao and Ping Guo and Chongfeng Guo and Zhaoyu Ren and Jintao Bai},
      title = {Coupling site controlled spin transport through the graphene nanoribbon junction: A first principles investigation},
      journal = {Computational Materials Science },
      year = {2015},
      volume = {99},
      pages = {203 - 208},
      doi = {http://dx.doi.org/10.1016/j.commatsci.2014.12.031}
    }
    
    M.A. Mehrabova, H.S. Orujov & N.H. Hasanov Ab initio study of defects in CdMnTe: Electronic structure and related properties 2014 International Journal of Materials Science and Applications
    Vol. 3(6-1), 24-32 
    DOI  
    Abstract: Band structure, density of states, total energy and magnetic moment are calculated for ideal and defective supercell CdTe and CdMnTe by ab initio method. The optimization of crystal structure and atom relaxation has been carried out. The band gap, local levels in the band gap and magnetic moments are defined for various defective supercell CdTe and CdMnTe in ferromagnetic and antiferromagnetic states. It has been defined that as Mn atoms, the vacancy, interstitial atom and Frenkel pair in the crystal structure form magnetic moment.
    Keywords: Semimagnetic Semiconductor, Electron Structure, Defect, Vacancy, Interstitial Atom, Frenkel Pair, Ab Initio, Magnetic Moment, Density of States, ATK, Application
    Area: materials
    BibTeX:
    @article{Mehrabova2014a,
      author = {M. A. Mehrabova and H. S. Orujov and N. H. Hasanov},
      title = {Ab initio study of defects in CdMnTe: Electronic structure and related properties},
      journal = {International Journal of Materials Science and Applications},
      year = {2014},
      volume = {3},
      number = {6-1},
      pages = {24-32},
      doi = {http://dx.doi.org/10.11648/j.ijmsa.s.2014030601.16}
    }
    
    M.A. Mehrabova, H.R. Nuriyev, H.S. Orujov, A.M. Nazarov, R.M. Sadigov & V.N. Poladova Defect formation energy for charge states and electrophysical properties of CdMnTe 2015 Proc. SPIE
    Vol. 9450Proc. SPIE, 94500Q-94500Q-10 
    DOI  
    Abstract: In this work the results of investigation of Cd1-xMnxTe (x=0.01, 0.03, 0.05) solid solutions synthesis and their thin films' obtaining technology have been represented. Epitaxial films of monocrystalline Cd1-xMnxTe semimagnetic semiconductors were obtained on mica substrate by MBC method. Lattice parameters and crystal structure of samples were defined with X-ray diffraction method. It has been studied the electrophysical parameters. Defect formation energy has been calculated for Cd1-xMnxTe semimagnetic semiconductors by Ab-initio method using Atomistix Toolkit program. We have studied the dependence of defect formation energy on supercell size for charged vacancy and interstitial defects in Cd1-xMnxTe thin films.
    Keywords: ATK; Application;
    Area: materials
    BibTeX:
    @inproceedings{Mehrabova2015,
      author = {Mehrabova, M. A. and Nuriyev, H. R. and Orujov, H. S. and Nazarov, A. M. and Sadigov, R. M. and Poladova, V. N.},
      title = {Defect formation energy for charge states and electrophysical properties of CdMnTe},
      booktitle = {Proc. SPIE},
      journal = {Proc. SPIE},
      year = {2015},
      volume = {9450},
      pages = {94500Q-94500Q-10},
      doi = {http://dx.doi.org/10.1117/12.2073343}
    }
    
    Serhan Yamacli Extraction of the voltage-dependent quantum capacitance and kinetic inductance of GNRFETs: a first-principles study 2014 Journal of Computational Electronics
    Vol. 14(1), 249-256 
    DOI  
    Abstract: Graphene nanoribbon field effect transistors (GNRFETs) are prominent candidates for the near future nanoelectronics technology. In this work, a sample GNRFET is simulated utilizing density functional theory with non-equilibrium Green's function formalism (NEGF) to obtain the current-voltage relationship, the variation of the channel charge and the electrostatic potential with respect to applied voltage. It is shown that a 5th order polynomial model, which can be utilized in circuit design tools, accurately models the current-voltage relationship of GNRFETs. More importantly, the variations of the kinetic inductance, quantum capacitance and the Fermi velocity dependent on both the source-drain (VDS) and source-gate voltages (VGS) are extracted. Numerical values of these parameters are found to be consistent with the theoretical and experimental average values existing in the literature. The paper is concluded with the discussion of the voltage-dependencies of the kinetic inductance and the quantum capacitance for the circuit design using GNRFETs.
    Keywords: GNRFET; Ab initio; Current-voltage relationship; Kinetic inductance; Quantum capacitance, ATK, Application
    Area: graphene
    BibTeX:
    @article{Yamacli2014d,
      author = {Yamacli, Serhan},
      title = {Extraction of the voltage-dependent quantum capacitance and kinetic inductance of GNRFETs: a first-principles study},
      journal = {Journal of Computational Electronics},
      publisher = {Springer US},
      year = {2014},
      volume = {14},
      number = {1},
      pages = {249-256},
      doi = {http://dx.doi.org/10.1007/s10825-014-0646-0}
    }
    
    Serhan Yamacli Voltage-Dependent Electronic Transport Properties of Reduced Graphene Oxide with Various Coverage Ratios 2015 Nano-Micro Letters
    Vol. 7(1), 42-50 
    DOI  
    Abstract: Graphene is mainly implemented by these methods: exfoliating, unzipping of carbon nanotubes, chemical vapour deposition, epitaxial growth and the reduction of graphene oxide. The latter option has the advantage of low cost and precision. However, reduced graphene oxide (rGO) contains hydrogen and/or oxygen atoms hence the structure and properties of the rGO and intrinsic graphene are different. Considering the advantages of the implementation and utilization of rGO, voltage-dependent electronic transport properties of several rGO samples with various coverage ratios are investigated in this work. Ab initio simulations based on density functional theory combined with non-equilibrium Green's function formalism are used to obtain the current-voltage characteristics and the voltage-dependent transmission spectra of rGO samples. It is shown that the transport properties of rGO are strongly dependent on the coverage ratio. Obtained results indicate that some of the rGO samples have negative differential resistance characteristics while normally insulating rGO can behave as conducting beyond a certain threshold voltage. The reasons of the peculiar electronic transport behaviour of rGO samples are further investigated, taking the transmission eigenstates and their localization degree into consideration. The findings of this study are expected to be helpful for engineering the characteristics of rGO structures.
    Keywords: Reduced graphene oxide; Coverage ratio; Negative differential resistance, ATK, Application
    Area: graphene
    BibTeX:
    @article{Yamacli2015,
      author = {Yamacli, Serhan},
      title = {Voltage-Dependent Electronic Transport Properties of Reduced Graphene Oxide with Various Coverage Ratios},
      journal = {Nano-Micro Letters},
      publisher = {Springer Berlin Heidelberg},
      year = {2015},
      volume = {7},
      number = {1},
      pages = {42-50},
      doi = {http://dx.doi.org/10.1007/s40820-014-0017-1}
    }
    
    X.F. Yang, Y.S. Liu, J.F. Feng, X.F. Wang, C.W. Zhang & F. Chi Transport properties of bare and hydrogenated zigzag silicene nanoribbons: Negative differential resistances and perfect spin-filtering effects 2014 Journal of Applied Physics
    Vol. 116(12), 124312 
    DOI  
    Abstract: Ab initio calculations are performed to investigate the spin-polarized transport properties of the bare and hydrogenated zigzag silicene nanoribbons (ZSiNRs). The results show that the ZSiNRs with symmetric (asymmetric) edges prefer the ferromagnetic (antiferromagnetic) as their ground states with the semiconductor properties, while the accordingly antiferromagnetic (ferromagnetic) states exhibit the metallic behaviors. These facts result in a giant magnetoresistance behavior between the ferromagnetic and antiferromagnetic states in the low bias-voltage regime. Moreover, in the ferromagnetic ZSiNRs with asymmetric edges, a perfect spin-filtering effect with 100% positive electric current polarization can be achieved by altering the bias voltage. In addition, we also find that the negative differential resistances prefer the metastable states. The findings here indicate that the asymmetric and symmetric ZSiNRs are promising materials for spintronic applications.
    Keywords: Antiferromagnetism, Ferromagnetism, Negative resistance, Atomic force microscopy, Fermi levels, ATK, Application
    Area: spintronics
    BibTeX:
    @article{Yang2014a,
      author = {Yang, X. F. and Liu, Y. S. and Feng, J. F. and Wang, X. F. and Zhang, C. W. and Chi, F.},
      title = {Transport properties of bare and hydrogenated zigzag silicene nanoribbons: Negative differential resistances and perfect spin-filtering effects},
      journal = {Journal of Applied Physics},
      year = {2014},
      volume = {116},
      number = {12},
      pages = {124312},
      doi = {http://dx.doi.org/10.1063/1.4896630}
    }
    
    X.F. Yang, X. Zhang, X.K. Hong, Y.S. Liu, J.F. Feng, X.F. Wang & C.W. Zhang Temperature-controlled giant thermal magnetoresistance behaviors in doped zigzag-edged silicene nanoribbons 2014 RSC Advances
    Vol. 4(89), 48539-48546 
    DOI  
    Abstract: Based on the nonequilibrium Green's function (NEGF) method combined with density functional theory (DFT), we investigate the spin-dependent thermoelectric transport properties of zigzag-edged silicene nanoribbons (ZSiNRs) doped by an Al-P bonded pair at different edge positions. For the ferromagnetic (FM) configuration, the strong quantum destructive interference effects between the localized states induced by the Al-P bonded pair and the side quantum states results in the appearance of spin-dependent transmission dips near the Fermi level. This fact leads to the simultaneous enhancement of the spin-filter efficiency and spin Seebeck coefficient at the Fermi level, while their signs are dependent on the doping positions. Moreover, for the antiferromagnetic (AFM) configuration, the spin-dependent transmission peaks with ordinary Lorentzian shapes near the Fermi level can be introduced by the Al-P bonded pair. Interestingly, a pure spin current in the doped AFM ZSiNRs can be achieved by modulating the temperature. In this case, the spin-filter efficiency can reach infinity, while the thermal magnetoresistance (TMR) between the FM and AFM configurations can also reach infinity.
    Keywords: ATK, Application, magnetoresistance, silicene, nanoribbon, thermoelectric transport, quantum interference effects, spin filter, Seebeck, ferromagnetic, antiferromagnetic
    Area: 2dmat, thermo
    BibTeX:
    @article{Yang2014c,
      author = {Yang, X. F. and Zhang, X. and Hong, X. K. and Liu, Y. S. and Feng, J. F. and Wang, X. F. and Zhang, C. W.},
      title = {Temperature-controlled giant thermal magnetoresistance behaviors in doped zigzag-edged silicene nanoribbons},
      journal = {RSC Advances},
      publisher = {Royal Society of Chemistry (RSC)},
      year = {2014},
      volume = {4},
      number = {89},
      pages = {48539-48546},
      doi = {http://dx.doi.org/10.1039/c4ra07791a}
    }
    
    C.H. Yang, X.Q. Deng, G.P. Tang & Z.Q. Fan Spin filtering behaviors for a carbon chain connected with armchair- and zigzag-edged graphene nanoribbon electrodes 2015 Solid State Communications
    Vol. 203, 26 - 30 
    DOI  
    Abstract: Using the non-equilibrium Green's function method combined with the density functional theory, we investigate the spin transport properties of carbon chains connected with armchair- and zigzag-edged graphene nanoribbon (ZGNR) electrodes at finite bias with the parallel magnetism configuration. When spin polarized electrons are injected into carbon chains from the ZGNR electrode, the beta;-spin current is nearly zero, while the &alpha;-spin current shows large values in the calculated bias region, thus the spin polarization 100% can be achieved, which is a promising pathway for developing a spin filter.
    Keywords: Spin filtering; Graphene; Carbon chain; First-principles calculation, ATK, Application
    Area: spintronics
    BibTeX:
    @article{Yang2015,
      author = {C.H. Yang and X.Q. Deng and G.P. Tang and Z.Q. Fan},
      title = {Spin filtering behaviors for a carbon chain connected with armchair- and zigzag-edged graphene nanoribbon electrodes },
      journal = {Solid State Communications },
      year = {2015},
      volume = {203},
      pages = {26 - 30},
      doi = {http://dx.doi.org/10.1016/j.ssc.2014.10.033}
    }
    
    Sheng Yu, Hao D. Xiong, Kwesi Eshun, Hui Yuan & Qiliang Li Phase transition, effective mass and carrier mobility of MoS2 monolayer under tensile strain 2015 Applied Surface Science
    Vol. 325, 27 - 32 
    DOI  
    Abstract: We report a computational study on the impact of tensile strain on MoS2 monolayer. The transition between direct and indirect bandgap structure and the transition between semiconductor and metal phases in the monolayer have been investigated with tensile strain along all direction configurations with both x-axis and y-axis components e_xy (e_x and e_y). Electron effective mass and the hole effective mass are isotropic for biaxial strain e_xy = e_x = e_y and anisotropic for e_xy with e_x != e_y. The carrier effective mass behaves differently along different directions in response to the tensile strain. In addition, the impact of strain on carrier mobility has been studied by using the deformation potential theory. The electron mobility increases over 10 times with the biaxial strain: e_x = e_y = 9.5%. Also, the mobility decreases monotonically with the increasing temperature as mu ~ 1/T. These results are very important for future nanotechnology based on two-dimensional materials.
    Keywords: Strain effect; Two-dimensional materials; MoS2 monolayer; Mobility enhancement; Phase transition, ATK, Application
    Area: 2dmat, tmd
    BibTeX:
    @article{Yu2015,
      author = {Sheng Yu and Hao D. Xiong and Kwesi Eshun and Hui Yuan and Qiliang Li},
      title = {Phase transition, effective mass and carrier mobility of MoS2 monolayer under tensile strain },
      journal = {Applied Surface Science},
      year = {2015},
      volume = {325},
      pages = {27 - 32},
      doi = {http://dx.doi.org/10.1016/j.apsusc.2014.11.079}
    }
    
    Pengfei Yuan, Wen Tian, Yongchang Zeng, Zhenhua Zhang & Junjun Zhang Electronic properties of one-dimensional graphene quantum-dot arrays 2014 Organic Electronics
    Vol. 15(12), 3577 - 3583 
    DOI  
    Abstract: Using the first-principles method based on density functional theory, the electronic properties of various one-dimensional graphene quantum-dot arrays (1D GQDAs) are systematically studied. It shows that arrays present semiconducting behaviors when their edge structure is armchair-type, however, if their edge structure is zigzag-type, arrays are either metallic or semiconducting depending on the type of edge units: AA-type or AB-type. Punching nanoholes in quantum-dots would lead to an increase of the band gap for semiconducting arrays, but does not change a metallicity significantly for metallic arrays. Moreover, we find that the band gap of 1D semiconducting GQDAs decreases oscillatorily with size increasing, which means that the bandgap size is closely related to the quantum confinement and size effects. Our studies show that constructing various kinds of 1D GQDAs can effectively regulate the electronic behaviors of the graphene structure and obtain abundant electrical properties.
    Keywords: One-dimensional graphene quantum-dot array, Electronic property, Bandgap, First-principles method, ATK, Application
    Area: graphene
    BibTeX:
    @article{Yuan2014,
      author = {Pengfei Yuan and Wen Tian and Yongchang Zeng and Zhenhua Zhang and Junjun Zhang},
      title = {Electronic properties of one-dimensional graphene quantum-dot arrays },
      journal = {Organic Electronics},
      year = {2014},
      volume = {15},
      number = {12},
      pages = {3577 - 3583},
      doi = {http://dx.doi.org/10.1016/j.orgel.2014.09.046}
    }
    
    Dan Zhang, Mengqiu Long, Xiaojiao Zhang, Can Cao, Hui Xu, Mingjun Li & Kowksum Chan Bipolar spin-filtering, rectifying and giant magnetoresistance effects in zigzag silicene nanoribbons with asymmetric edge hydrogenation 2014 Chemical Physics Letters
    Vol. 616-617, 178 - 183 
    DOI  
    Abstract: Using the nonequilibrium Green's function method and the spin-polarized density functional theory, the spin-dependent electronic transport properties of zigzag silicene nanoribbons (ZSiNRs) with asymmetric edge hydrogenation have been studied. The results show that there exists nearly 100% bipolar spin-filtering behavior in the ZSiNR-based devices with antiparallel spin configuration. Moreover, rectifying behavior and giant magnetoresistance are found in the devices. Our calculation suggests ZSiNRs with asymmetric edge hydrogenation as a promising candidate material for spintronics.
    Keywords: ATK, Application, spin filtering, giant magnetoresistance, silicene, nanoribbon, edge hydrogenation, rectification
    Area: 2dmat, spin
    BibTeX:
    @article{Zhang2014a,
      author = {Dan Zhang and Mengqiu Long and Xiaojiao Zhang and Can Cao and Hui Xu and Mingjun Li and Kowksum Chan},
      title = {Bipolar spin-filtering, rectifying and giant magnetoresistance effects in zigzag silicene nanoribbons with asymmetric edge hydrogenation},
      journal = {Chemical Physics Letters},
      year = {2014},
      volume = {616-617},
      pages = {178 - 183},
      doi = {http://dx.doi.org/10.1016/j.cplett.2014.10.041}
    }
    
    Wu-Xing Zhou & Ke-Qiu Chen Enhancement of Thermoelectric Performance by Reducing Phonon Thermal Conductance in Multiple Core-shell Nanowires 2014 Scientific Reports
    Vol. 4, 7150 
    DOI  
    Abstract: The thermoelectric properties of multiple core-shell nanowires are investigated by using nonequilibrium Green's function method and molecular dynamics simulations. The results show that the thermoelectric performance of multiple core-shell NWs can be improved observably with the increase of shell number compared with the single component NWs due to the significant reduction of phonon thermal conductance. The ZT value of multiple core-shell NWs can reach three times greater than that of the single component GaSb NWs at room temperature. Moreover, the ZT values of both the core-shell NWs and single component NWs are increased with the increasing temperature, but the ZT value of core-shell NWs increases more slowly than that of single component NWs. These results show that the single component NWs is suitable as thermoelectric material at much high temperature, but the multiple core-shell NWs is more suitable as thermoelectric material at room temperature.
    Keywords: Electronic properties and materials, Nanowires, ATK, Application
    Area: nanowires, thermo
    BibTeX:
    @article{Zhou2014,
      author = {Zhou, Wu-Xing and Chen, Ke-Qiu},
      title = {Enhancement of Thermoelectric Performance by Reducing Phonon Thermal Conductance in Multiple Core-shell Nanowires},
      journal = {Scientific Reports},
      publisher = {Nature Publishing Group},
      year = {2014},
      volume = {4},
      pages = {7150},
      doi = {http://dx.doi.org/10.1038/srep07150}
    }
    
    Brahim Akdim, Ruth Pachter & Richard A. Vaia Tunability in electron transport of molybdenum chalcogenide nanowires by theoretical prediction 2014 Chemical Physics Letters
    Vol. 615, 99 - 104 
    DOI  
    Abstract: Transition metal chalcogenide nanowires could comprise an alternative for nanoelectronics application, yet this class of materials is not well-characterized. Here we predict tunability in I-V characteristics of MoX (X = S, Se) nanowires, dependent on chalcogen atom, Li doping, type of electrode, and morphology. We show an intrinsic negative differential resistance (NDR)-like behavior for Mo6S6 nanowires, explained by bands mismatch in the electronic structure calculated by density functional theory (DFT) within the non-equilibrium Green's function formalism. The NDR-like behavior is suppressed upon Li intercalation or for gold leads. The electron transport results are based on optimized configurations using a non-empirical London dispersion-corrected DFT functional.
    Keywords: ATK, Application, transition metal chalcogenide, negative differential resistance, nanowires, van der Waals, dispersion
    Area: 2dmat, nanowires, tmd
    BibTeX:
    @article{Akdim2014,
      author = {Brahim Akdim and Ruth Pachter and Richard A. Vaia},
      title = {Tunability in electron transport of molybdenum chalcogenide nanowires by theoretical prediction },
      journal = {Chemical Physics Letters },
      year = {2014},
      volume = {615},
      pages = {99 - 104},
      doi = {http://dx.doi.org/10.1016/j.cplett.2014.10.011}
    }
    
    A.S. Azman, Z. Johari & R. Ismail Performance evaluation of dual-channel armchair graphene nanoribbon field-effect transistor 2014 2014 IEEE International Conference on Semiconductor Electronics, 138-141  DOI  
    Abstract: Graphene has become a potential successor to silicon in electronic devices. In this paper, the performance of dual-channel armchair graphene nanoribbon field-effect transistor (AGNR FET) is investigated. Both physical and electrical properties of dual-channel AGNR FET are simulated using Atomistic Tool Kit from Quantum Wise. Their band structures and transmission spectra are analyzed. Current-voltage characteristic is then extracted and the performance of single and dual-channel AGNR FETs is compared. From the simulation, it is found that dual-channel AGNR FET exhibits significant improvement in ON current over two fold. Results obtained will give insight in the implementation of dual-channel AGNR FET for performance enhancement in future electronic devices.
    Keywords: field effect transistors;graphene;nanoribbons;ON current;atomistic tool kit;band structures;current-voltage characteristic;dual-channel armchair graphene nanoribbon field-effect transistor;electrical properties;electronic devices;performance evaluation;physical properties;quantum wise;single channel AGNR FET;transmission spectra;Arrays;Electrodes;Field effect transistors;Graphene;Performance evaluation;Photonic band gap;armchair graphene nanoribbon;dual-channel;field-effect transistor, ATK, Application
    Area: graphene, nanoribbons
    BibTeX:
    @inproceedings{Azman2014a,
      author = {Azman, A.S. and Johari, Z. and Ismail, R.},
      title = {Performance evaluation of dual-channel armchair graphene nanoribbon field-effect transistor},
      booktitle = {2014 IEEE International Conference on Semiconductor Electronics},
      year = {2014},
      pages = {138-141},
      doi = {http://dx.doi.org/10.1109/SMELEC.2014.6920815}
    }
    
    Zhaoqiang Bai, Lei Shen, Yongqing Cai, Qingyun Wu, Minggang Zeng, Guchang Han & Yuan Ping Feng Magnetocrystalline anisotropy and its electric-field-assisted switching of Heusler-compound-based perpendicular magnetic tunnel junctions 2014 New Journal of Physics
    Vol. 16(10), 103033 
    DOI  
    Abstract: Employing density functional theory combined with the non-equilibrium Green's function formalism, we systematically investigate the structural, magnetic and magnetoelectric properties of the Co2FeAl(CFA)/MgO interface, as well as the spin-dependent transport characteristics of the CFA/MgO/CFA perpendicular magnetic tunnel junctions (p-MTJs). We find that the structure of the CFA/MgO interface with the oxygen-top FeAl termination has high thermal stability, which is protected by the thermodynamic equilibrium limit. Furthermore, this structure is found to have perpendicular magnetocrystalline anisotropy (MCA). Giant electric-field-assisted modifications of this interfacial MCA through magnetoelectric coupling are demonstrated with an MCA coefficient of up to 1E-7 erg / V cm. In addition, our non-collinear spin transport calculations of the CFA/MgO/CFA p-MTJ predict a good magnetoresistance performance of the device.
    Keywords: Heusler alloy, magnetic crystalline anisotropy, magnetoelectric effect, magnetic tunnel junction, non-collinear spin transport, ATK, Application
    Area: interfaces, spin, nvm
    BibTeX:
    @article{Bai2014,
      author = {Zhaoqiang Bai and Lei Shen and Yongqing Cai and Qingyun Wu and Minggang Zeng and Guchang Han and Yuan Ping Feng},
      title = {Magnetocrystalline anisotropy and its electric-field-assisted switching of Heusler-compound-based perpendicular magnetic tunnel junctions},
      journal = {New Journal of Physics},
      year = {2014},
      volume = {16},
      number = {10},
      pages = {103033},
      doi = {http://dx.doi.org/10.1088/1367-2630/16/10/103033}
    }
    
    S. Caliskan & S. Guner The role of Co atoms in spin dependent electronic properties of graphite-like ZnO structures 2015 Journal of Magnetism and Magnetic Materials
    Vol. 373, 96 - 102 
    DOI  
    Abstract: A first principles study is employed to reveal the electronic properties of graphite-like Co doped ZnO structures composed of atomic layers when spin property of electrons is involved. The influence of Co atoms, which are substituting the Zn atoms, was addressed through distinct atomic arrangements formed by specific atomic configurations and various Co concentrations. We obtained that the spin dependent behavior is largely determined by the atomic arrangement which can crucially impact the electronic structure for a certain spin orientation. It was observed that atomic configuration is an essential factor which may reduce or enhance the minority-spin energy gap relative to majority one. It was shown that the emerging spin polarization can be manipulated by the atomic arrangement of the layered structures. Both the spin polarization and the magnetic moment were found to be contributed by both Co and O atoms. The stability of a system via formation energy, the role of Co dopants positioned at different Zn sites, the number of both Co atoms and layers in a supercell, and the mechanisms governing the spin dependent behavior of these structures are discussed.
    Keywords: First principles, Density functional theory, Density of state, Doped ZnO, ATK, Application
    Area: 2dmat, spin
    BibTeX:
    @article{Caliskan2015,
      author = {S. Caliskan and S. Guner},
      title = {The role of Co atoms in spin dependent electronic properties of graphite-like ZnO structures },
      journal = {Journal of Magnetism and Magnetic Materials},
      year = {2015},
      volume = {373},
      pages = {96 - 102},
      note = {Recent Advances in Nanomagnetism and Spintronics },
      doi = {http://dx.doi.org/10.1016/j.jmmm.2014.05.039}
    }
    
    Anuja Chanana & Santanu Mahapatra First principles study of metal contacts to monolayer black phosphorous 2014 Journal of Applied Physics
    Vol. 116(20), 204302 
    DOI  
    Abstract: Atomically thin layered black phosphorous (BP) has recently appeared as an alternative to the transitional metal di chalcogenides for future channel material in a MOS transistor due to its lower carrier effective mass. Investigation of the electronic property of source/drain contact involving metal and two-dimensional material is essential as it impacts the transistor performance. In this paper we perform a systematic and rigorous study to evaluate the Ohmic nature of the side-contact formed by the monolayer BP (mBP) and metals (gold, titanium and palladium), which are commonly used in experiments. Employing the Density Functional Theory (DFT), we analyse the potential barrier, charge transfer and atomic orbital overlap at the metal-mBP interface in an optimized structure to understand how efficiently carriers could be injected from metal contact to the mBP channel. Our analysis shows that gold forms a Schottky contact with a higher tunnel barrier at the interface in comparison to the titanium and palladium. mBP contact with palladium is found to be purely Ohmic, where as titanium contact demonstrates an intermediate behaviour.
    Keywords: ATK, Application, metal contacts, black phosphorous, MOS transistor, Ohmic contact, Schottky barrier
    Area: 2dmat, interfaces
    BibTeX:
    @article{Chanana2014,
      author = {Chanana, Anuja and Mahapatra, Santanu},
      title = {First principles study of metal contacts to monolayer black phosphorous},
      journal = {Journal of Applied Physics},
      year = {2014},
      volume = {116},
      number = {20},
      pages = {204302},
      doi = {http://dx.doi.org/10.1063/1.4901998}
    }
    
    Tong Chen, Lingling Wang, Xiaofei Li, Kaiwu Luo, Liang Xu, Quan Li, Xianghua Zhang & Mengqiu Long Spin-dependent transport properties of a chromium porphyrin-based molecular embedded between two graphene nanoribbon electrodes 2014 RSC Advances
    Vol. 4, 60376-60381 
    DOI  
    Abstract: By using the non-equilibrium Green's function formalism combined with density-functional theory, we present a theoretical study of the spin-dependent electron transport of a molecular device constructed from a chromium porphyrin molecule linking with two carbon chains sandwiched between two semi-infinite zigzag-edged graphene nanoribbon (ZGNR) electrodes, where the ZGNRs are modulated by an external magnetic field. The results show that the single spin-conducting can be obtained by performing different magnetic configuration of the leads. The coexistence of spin-filtering with 100% spin-polarization, rectifying and negative differential resistance (NDR) behaviors in our model device is demonstrated and mechanisms are proposed for these phenomena.
    Keywords: ATK, Application, chromium porphyrin, graphene nanoribbon, spin filtering, rectification, negative differential resistance
    Area: graphene, spintronics
    BibTeX:
    @article{Chen2014c,
      author = {Chen, Tong and Wang, Lingling and Li, Xiaofei and Luo, Kaiwu and Xu, Liang and Li, Quan and Zhang, Xianghua and Long, Mengqiu},
      title = {Spin-dependent transport properties of a chromium porphyrin-based molecular embedded between two graphene nanoribbon electrodes},
      journal = {RSC Advances},
      publisher = {The Royal Society of Chemistry},
      year = {2014},
      volume = {4},
      pages = {60376-60381},
      doi = {http://dx.doi.org/10.1039/C4RA09279A}
    }
    
    Jue-Fei Cheng, Liping Zhou, Man Liu, Qiang Yan, Qin Han & Lei Gao Tip-contact related low-bias negative differential resistance and rectifying effects in benzene-porphyrin-benzene molecular junctions 2014 The Journal of Chemical Physics
    Vol. 141(17), 174304 
    DOI  
    Abstract: The electronic transport properties of benzene-porphyrin-benzene (BPB) molecules coupled to gold (Au) electrodes were investigated. By successively removing the front-end Au atoms, several BPB junctions with different molecule-electrode contact symmetries were constructed. The calculated current-voltage (I-V) curves depended strongly on the contact configurations between the BPB molecules and the Au electrodes. In particular, a significant low-voltage negative differential resistance effect appeared at -0.3 V in the junctions with pyramidal electrodes on both sides. Along with the breaking of this tip-contact symmetry, the low-bias negative differential resistance effect gradually disappeared. This tip-contact may be ideal for use in the design of future molecular devices because of its similarity with experimental processes.
    Keywords: Electrodes, Gold, Negative differential resistance, Fermi levels, Transport properties, ATK, Application, rectification
    Area: molecular electronics
    BibTeX:
    @article{Cheng2014,
      author = {Cheng, Jue-Fei and Zhou, Liping and Liu, Man and Yan, Qiang and Han, Qin and Gao, Lei},
      title = {Tip-contact related low-bias negative differential resistance and rectifying effects in benzene-porphyrin-benzene molecular junctions},
      journal = {The Journal of Chemical Physics},
      year = {2014},
      volume = {141},
      number = {17},
      pages = {174304},
      doi = {http://dx.doi.org/10.1063/1.4900630}
    }
    
    X.Q. Deng, Z.H. Zhang, G.P. Tang, Z.Q. Fan & C.H. Yang Electronic and spin transport properties in zigzag silicene nanoribbons with edge protrusions 2014 RSC Advances
    Vol. 4, 58941-58948 
    DOI  
    Abstract: We investigate the electronic transport properties of zigzag-edged silicene nanoribbons (ZSiNRs) with one or two protrusions at the edges using the density functional theory combined with nonequilibrium Green's function method. It is found that the protrusion generally breaks down the edge state along the same edge, which carries current in the junction. For the ZSiNR having an even number of zigzag chains in its width, the protrusions can increase the conductance except for the case of two symmetric protrusions. For ZSiNRs with an odd number of zigzag chains in its width, the introduction of edge protrusions can suppress currents. We also investigate the spin-dependent transport properties of ZSiNR-based devices with antiparallel (AP) magnetism configuration. Interestingly, only non- and symmetric-protrusion models with a width of an even number of zigzag chains show a perfect spin filter effect.
    Keywords: ATK, Application, silicene, nanoribbon, spin filtering
    Area: 2dmat
    BibTeX:
    @article{Deng2014b,
      author = {Deng, X. Q. and Zhang, Z. H. and Tang, G. P. and Fan, Z. Q. and Yang, C. H.},
      title = {Electronic and spin transport properties in zigzag silicene nanoribbons with edge protrusions},
      journal = {RSC Advances},
      publisher = {The Royal Society of Chemistry},
      year = {2014},
      volume = {4},
      pages = {58941-58948},
      doi = {http://dx.doi.org/10.1039/C4RA09566A}
    }
    
    Bahniman Ghosh, Abhishek Gupta & Bhupesh Bishnoi Effects of defects on the electronic properties of WTe 2 armchair nanoribbons 2014 J. Semicond.
    Vol. 35(11), 113002 
    DOI  
    Abstract: We have investigated the electronic properties of WTe2 armchair nanoribbons with defects. WTe2 nanoribbons can be categorized depending on the edge structure in two types: armchair and zigzag. WTe2 in its bulk form has an indirect band gap but nanoribbons and nanosheets of WTe2 have direct band gaps. Interestingly, the zigzag nanoribbon is metallic while the armchair nanoribbons are semiconducting. Thus they can find applications in device fabrication. Therefore, it is very important to study the effect of defects on the electronic properties of the armchair nanoribbons as these defects can impair the device properties and characteristics. We have considered defects such as: vacancy, rough edge, wrap, ripple and twist in this work. We report the band gap variation with these defects. We have also studied the change in band gap and total energy with varying degrees of wrap, ripple and twist.
    Keywords: electronic property; WTe2, nanoribbon; defects, ATK, Application, band gap
    Area: 2dmat, tmd
    BibTeX:
    @article{Ghosh2014a,
      author = {Ghosh, Bahniman and Gupta, Abhishek and Bishnoi, Bhupesh},
      title = {Effects of defects on the electronic properties of WTe 2 armchair nanoribbons},
      journal = {J. Semicond.},
      publisher = {IOP Publishing},
      year = {2014},
      volume = {35},
      number = {11},
      pages = {113002},
      doi = {http://dx.doi.org/10.1088/1674-4926/35/11/113002}
    }
    
    L. Gong, S.L. Xiu, M.M. Zheng, P. Zhao, Z. Zhang, Y.Y. Liang, G. Chen & Y. Kawazoe Electronic properties of silicene superlattices: roles of degenerate perturbation and inversion symmetry breaking 2014 J. Mater. Chem. C
    Vol. 2(41), 8773-8779 
    DOI  
    Abstract: Using both the first-principles method and the tight-binding method, we have carried out detailed studies on the electronic properties of silicene superlattices. According to the band-folding picture, in the hexagonal silicene superlattice (M,N) when both M and N are integer multiples of 3, the simultaneous folding of K and K' points to the &gamma; point results in the fourfold degeneracy. In the orthogonal one [P,Q], the fourfold degeneracy occurs if Q = 3q (q is an integer) is satisfied. By introducing degenerate perturbation to remove the fourfold degeneracy, the bandgap could be opened no matter whether the inversion symmetry remains or not. For the other cases, the bandgaps could be kept closed by the inversion symmetry preservation. Besides, the studied transport properties confirm the bandgap tuning by applying degenerate perturbation to the silicene superlattice. The new bandgap opening mechanism with degenerate perturbation could benefit further experimental studies of the silicene-based nanostructures for applications in nanoelectronics.
    Keywords: ATK, Application, silicene superlattice, degenerate pertubation, inversion symmetry breaking, band gap opening
    Area: semi
    BibTeX:
    @article{Gong2014,
      author = {Gong, L. and Xiu, S. L. and Zheng, M. M. and Zhao, P. and Zhang, Z. and Liang, Y. Y. and Chen, G. and Kawazoe, Y.},
      title = {Electronic properties of silicene superlattices: roles of degenerate perturbation and inversion symmetry breaking},
      journal = {J. Mater. Chem. C},
      publisher = {Royal Society of Chemistry (RSC)},
      year = {2014},
      volume = {2},
      number = {41},
      pages = {8773-8779},
      doi = {http://dx.doi.org/10.1039/c4tc01665c}
    }
    
    C. Preferencial Kala, P. Aruna Priya & D. John Thiruvadigal Role of side groups and temperature dependent studies in a molecular device 2015 Journal of Computational Electronics
    Vol. 14(1), 240-248 
    DOI  
    Abstract: The quantum transport through Tour Wires (TWs) functionalized with different side groups was studied using nonequilibrium Green's function formalism combined with extended Huckel theory. Au-TW-Au junctions were constructed with functional groups NO2 and NH2. The transmission spectrum and the isosurface of transmission eigen channel at the HOMO resonance and the LUMO resonance shows that the resonant transmission peaks are related to the delocalized nature of the &pi;-orbitals of the TWs that was not much affected by the functionalization at room temperature. Furthermore, the influence of the temperature effect on the transport characteristics have been emphasized, and the result shows that for the TW and TW-NH2 systems conductance increase with increasing temperature indicating the dominating transport mechanism which is due to thermionic emission. The temperature dependence arises from the thermal spreading in the leads but also from a thermal average over the different configurations. In particular, negative differential resistance nature was observed for TW-NO2 at the temperature of 100 K in the positive and the negative bias region.
    Keywords: Molecular electronics; Extended Huckel theory (EHT); Non-equlibrium Green's function (NEGF); Quantum transport, ATK-SE, Application, negative differential resistance
    Area: molecular electronics
    BibTeX:
    @article{Kala2015,
      author = {Kala, C. Preferencial and Aruna Priya, P. and John Thiruvadigal, D.},
      title = {Role of side groups and temperature dependent studies in a molecular device},
      journal = {Journal of Computational Electronics},
      publisher = {Springer US},
      year = {2015},
      volume = {14},
      number = {1},
      pages = {240-248},
      doi = {http://dx.doi.org/10.1007/s10825-014-0644-2}
    }
    
    W.H. Khoo & S.M. Sultan A study on the gas sensing effect on current-voltage characteristics of ZnO nanostructures 2014 2014 IEEE International Conference on Semiconductor Electronics, 221-224  DOI  
    Abstract: Current-voltage characteristics of ZnO nanostructures were studied under different gas ambient using nonequilibrium Green's function and density functional theory, DFT technique. It was found that I-V characteristics of ZnO nanostructures depend strongly on the type of gas molecules present. The sensitivity factor of more than 200% achieved with the presence of a single molecule of NO2 gas. Meanwhile, there were no significant changes towards CO and NH3 gas molecules. However, CO adsorption can significantly suppress the transmission spectrum of ZnO nanostructures. Under the same applied bias voltage, the current through ZnO nanostructures decreases with increasing CO concentrations.
    Keywords: Green's function methods;II-VI semiconductors;ammonia;carbon compounds;density functional theory;gas sensors;nanosensors;nanostructured materials;nitrogen compounds;zinc compounds;CO;DFT technique;I-V characteristics;NH3;NO2;ZnO;bias voltage;current-voltage characteristics;density functional theory;gas molecule;gas sensing effect;nanostructure;nonequilibrium Green's function;sensitivity factor;Adsorption;Current-voltage characteristics;Electrodes;Nanowires;Scattering;Zinc oxide;DFT;Quantum Wise;ZnOApplication, ATK, Application
    Area: 2dmat
    BibTeX:
    @inproceedings{Khoo2014,
      author = {Khoo, W.H. and Sultan, S.M.},
      title = {A study on the gas sensing effect on current-voltage characteristics of ZnO nanostructures},
      booktitle = {2014 IEEE International Conference on Semiconductor Electronics},
      year = {2014},
      pages = {221-224},
      doi = {http://dx.doi.org/10.1109/SMELEC.2014.6920836}
    }
    
    Xiangru Kong, Bin Cui, Wenkai Zhao, Jingfen Zhao, Dongmei Li & Desheng Liu Spin negative differential resistance and high spin filtering behavior realized by devices based on graphene nanoribbons and graphitic carbon nitrides 2014 Organic Electronics
    Vol. 15(12), 3674 - 3680 
    DOI  
    Abstract: Using nonequilibrium Green's functions in combination with the density functional theory, we investigate the spin-dependent electronic transport properties of two nanostructure devices based on graphitic carbon nitrides bridging two zigzag graphene nanoribbons, i.e., center and edge bridged devices, respectively. It is found that the center bridged device behaves spin negative differential resistance properties in different bias ranges for the up and down spin current respectively. The edge bridged device presents obvious negative differential resistance only for the down spin current. Moreover, high spin-filtering efficiency over 80% is obtained in the edge bridged device in the bias range of 0-1.0 V. The magnetic properties of these devices suggest promising applications in spintronics and molecular electronics.
    Keywords: First-principles calculation, Graphene nanoribbons, Negative differential resistance, Spin filtering behavior, ATK, Application
    Area: graphene, spin
    BibTeX:
    @article{Kong2014,
      author = {Xiangru Kong and Bin Cui and Wenkai Zhao and Jingfen Zhao and Dongmei Li and Desheng Liu},
      title = {Spin negative differential resistance and high spin filtering behavior realized by devices based on graphene nanoribbons and graphitic carbon nitrides },
      journal = {Organic Electronics },
      year = {2014},
      volume = {15},
      number = {12},
      pages = {3674 - 3680},
      doi = {http://dx.doi.org/10.1016/j.orgel.2014.10.016}
    }
    
    Xiaobo Li, Hao Gao, Haiqing Wan, Hui-Li Li & Guanghui Zhou A multi-functional molecular device based on oligo phenylenevinylene and graphene 2014 Chemical Physics Letters
    Vol. 610-611, 298 - 302 
    DOI  
    Abstract: Using ab initio method, we study the electronic transport for a molecular device consisting of an oligo(p-phenylenevinylene) (OPV) molecule sandwiched between two zigzag-edged graphene nanoribbon (ZGNR) electrodes. Interestingly, a number of electrical functions, including switching, spin-filtering, negative differential resistance and spin-diode, are numerically observed in the device with different OPV conformations respect to ZGNRs and spin configurations in two electrodes. By analyzing the spatial distribution of local density of states, the performance of spin-filtering and -rectifying is explained to the asymmetry distribution of the central molecular orbitals as well as the corresponding coupling to the electrodes.
    Keywords: ATK, Application, oligo phenylenevinylene, graphene, electronic transport, nanoribbon, spin filtering, switching, negative differential resistance, spin diod, local density of states.
    Area: molecular electronics
    BibTeX:
    @article{Li2014c,
      author = {Xiaobo Li and Hao Gao and Haiqing Wan and Hui-Li Li and Guanghui Zhou},
      title = {A multi-functional molecular device based on oligo phenylenevinylene and graphene },
      journal = {Chemical Physics Letters },
      year = {2014},
      volume = {610-611},
      pages = {298 - 302},
      doi = {http://dx.doi.org/10.1016/j.cplett.2014.07.055}
    }
    
    Y.C. Lin & P.W. Chiu Graphene: Properties, Preparation, Characterisation and Devices 2014 Graphene, 265-291  DOI  
    Abstract: The effects of polymer and metal adsorbates on charge transport in graphene are reviewed to show how such surface contamination has long been a critical obstacle to using graphene for unique applications that require large-area and extra-clean fl atlands, such as sample supports for electron microscope studies of molecules, single-molecule resolution chemical sensors and biosensors, and ultrahigh- speed electronics. An optical approach is used to determine the density/coverage of the adsorbates and ways of removing unwanted polymer residues are investigated.
    Keywords: Application, electron mobility, polymers, contamination, metals, graphene, ATK
    Area: graphene
    BibTeX:
    @inbook{Lin2014,
      author = {Lin, Y.C. and Chiu, P.W.},
      title = {Graphene: Properties, Preparation, Characterisation and Devices},
      journal = {Graphene},
      publisher = {Elsevier},
      year = {2014},
      pages = {265-291},
      doi = {http://dx.doi.org/10.1533/9780857099334.3.265}
    }
    
    Ahmed Mahmoud & Paolo Lugli Atomistic study on dithiolated oligo-phenylenevinylene gated device 2014 Journal of Applied Physics
    Vol. 116(20), 204504 
    DOI  
    Abstract: Thanks to their semiconducting behavior, conjugated molecules are considered as an attractive candidate for future electronic devices. Understanding the charge transport characteristics through such molecules for different device applications would accelerate the progress in the field of molecular electronics. In addition, it would become more feasible to introduce/enhance specific properties of molecular devices. This theoretical paper focuses on atomistic simulation and characterization of novel molecular FET employing dithiolated oligo-phenylenevinylene molecules. The simulation is validated by its agreement with the experimental measurements conducted on the same molecules. The employed molecule has oxygen linkers, which are responsible for the strongly nonlinear current characteristics on the molecular device. We perform a thorough atomistic device analysis to illustrate the principles behind the nonlinear current characteristics and the gating effect.
    Keywords: Electrodes, Carrier density, Density functional theory, III-V semiconductors, General molecular properties, ATK, Application
    Area: molecular electronics
    BibTeX:
    @article{Mahmoud2014,
      author = {Mahmoud, Ahmed and Lugli, Paolo},
      title = {Atomistic study on dithiolated oligo-phenylenevinylene gated device},
      journal = {Journal of Applied Physics},
      year = {2014},
      volume = {116},
      number = {20},
      pages = {204504},
      doi = {http://dx.doi.org/10.1063/1.4902861}
    }
    
    M.V. Manasa, K. Venkateswara Rao & K. Bikshalu Synthesis, Characterization of Nanoscale Lanthanum Aluminate and Simulation of Nanoscale Metal Oxide Semiconductor Devices 2014 Advanced Science, Engineering and Medicine
    Vol. 6(10), 1111-1117 
    DOI  
    Abstract: The zeal to allow much higher density of logic gates/logic functions on extremely small chip, needed to scale down the Complementary Metal Oxide Semiconductor (CMOS) transistors to nano scale (1 nm to 100 nm). Thus the scaling of CMOS transistor requires replacement of the conventional silica gate oxide (SiO2) or oxy nitride (SiON) with a higher dielectric constant (K) gate dielectric to minimize the leakage current and to maintain a large capacitance especially at nano level to escape Quantum Mechanical Tunneling. Among several contenders, lanthanum aluminium oxide/lanthanum aluminate (LaAlO3 is the suitable successor of the conventional gate dielectric as it combines the advantages of high dielectric constant of lanthana (La2O3) and chemical, thermal stability of alumina (Al2O3). Hence synthesis of lanthanum aluminate nanoparticles was done by Gelation-Precipitation method and were characterized by X ray Diffractometer (XRD), Particle Size Analyzer (PSA), Thermo Gravimetry/Differential Thermal Analysis (TG/DTA), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). We also present a work on simulation of two Metal Oxide Semiconductor Field Effect Transistors (MOSFETs); one with nano silica oxide layer and other with nano lanthanum aluminate oxide layer. We compare the I-V characteristics, Transmission spectra and conductance of both the MOSFETs to show that the output current of MOSFET using nano LaAlO3 oxide layer is higher compared to that of the MOSFET using nano SiO2 oxide layer.
    Keywords: conductance; gelation-precipitation; i-v characteristics; lanthanum aluminate (laalo3 ); mosfet; oxide layer; sio2 (silica); transmission spectrum; ATK; Application
    Area: semi, interfaces
    BibTeX:
    @article{Manasa2014,
      author = {Manasa, M. V. and Rao, K. Venkateswara and Bikshalu, K.},
      title = {Synthesis, Characterization of Nanoscale Lanthanum Aluminate and Simulation of Nanoscale Metal Oxide Semiconductor Devices},
      journal = {Advanced Science, Engineering and Medicine},
      year = {2014},
      volume = {6},
      number = {10},
      pages = {1111-1117},
      doi = {http://dx.doi.org/10.1166/asem.2014.1567}
    }
    
    M Manoharan & Hiroshi Mizuta Edge irregularities in extremely down-scaled graphene nanoribbon devices: role of channel width 2014 Materials Research Express
    Vol. 1(4), 045605 
    URL 
    Abstract: When it comes to extremely downscaled graphene device research, it is imperative to develop a comprehensive understanding of what kinds of edge irregularities are likely to occur in the realistic graphene nanoribbons (GNRs) as well as their impact on the electronic and transport properties of GNRs. Here we present the first-principle calculations of the formation energy of the edge vacancies and protrusions in the armchair GNRs (AGNRs) with widths ranging from 9 to 12 carbon atoms and zigzag GNRs (ZGNRs). We also examine their influence on the electronic states and transport characteristics of the GNRs. The formation energy calculations show that double vacancy (DV) edge defects and zigzag protrusions are the most likely edge irregularities in the AGNRs. The DV edge defects increase the bandgap in 11-AGNRs and decrease the bandgap in 9, 10, 12-AGNRs. Zigzag protrusions widen the bandgap in 9, 12-AGNRs and reduce the bandgap in 10, 11-AGNRs. Edge defects induced wave function localization leads to the anti-resonant transmission characteristics. Edges of the ZGNRs show a high tendency to be modified by the exothermic effect. However, their current carrying capacity is not compromised by the edge irregularities.
    Keywords: ATK, application, graphene nanoribbon, vacancy formation energy, band gap
    Area: graphene
    BibTeX:
    @article{Manoharan2014,
      author = {M Manoharan and Hiroshi Mizuta},
      title = {Edge irregularities in extremely down-scaled graphene nanoribbon devices: role of channel width},
      journal = {Materials Research Express},
      year = {2014},
      volume = {1},
      number = {4},
      pages = {045605},
      url = {http://stacks.iop.org/2053-1591/1/i=4/a=045605}
    }
    
    Yukihito Matsuura Spin conduction in nitroxide molecules 2015 Chemical Physics Letters
    Vol. 619, 23 - 26 
    DOI URL 
    Abstract: Spin conduction by a molecule-containing nitroxide radicals linked via a phenylene coupling unit was estimated by calculating the transmission of electrons in the molecule when sandwiched between two semi-infinite periodic gold crystals. Nitroxides linked via a m-phenylene coupling unit showed a large splitting in the energy of the transmission peaks of alpha;- and beta;-spins, whereas this energy splitting was smaller for molecules with extended &pi;-conjugation, such as nitroxides linked via a p-phenylene coupling unit. The energy splitting of transmission is influenced by spin polarization and constructive/destructive interference of radicals through the phenylene coupling unit.
    Keywords: ATK, Application, spin conduction, nitroxide radical
    Area: molecular electronics, spin
    BibTeX:
    @article{Matsuur2015,
      author = {Yukihito Matsuura},
      title = {Spin conduction in nitroxide molecules },
      journal = {Chemical Physics Letters},
      year = {2015},
      volume = {619},
      pages = {23 - 26},
      url = {http://www.sciencedirect.com/science/article/pii/S0009261414009749},
      doi = {http://dx.doi.org/10.1016/j.cplett.2014.11.030}
    }
    
    R. Nigam, S. Habeeb, A. Priyadarshi & N. Jaggi Electrical conductivity of metal-carbon nanotube structures: Effect of length and doping 2014 Bulletin of Materials Science
    Vol. 37(5), 1047-1051 
    DOI  
    Abstract: The electrical properties of asymmetric metal-carbon nanotube (CNT) structures have been studied using density functional theory and non-equilibrium Green's function method with Atomistix tool kit. The models with asymmetric metal contacts and carbon nanotube bear resemblance to experimental set-ups. The study shows the effect of varying length of carbon nanotube on electronic transmission and conductance of various structures. The effects of silicon doping on CNT-based structures have also been studied. The conductance of structure with longer CNT is more compared with shorter CNT. Silicon doping increases the conductivity of carbon nanotube-based structure.
    Keywords: Density functional theory; non-equilibrium green function; carbon nanotube; silicon; Application, ATK, Application
    Area: nanotubes
    BibTeX:
    @article{Nigam2014,
      author = {Nigam, R. and Habeeb, S. and Priyadarshi, A. and Jaggi, N.},
      title = {Electrical conductivity of metal-carbon nanotube structures: Effect of length and doping},
      journal = {Bulletin of Materials Science},
      publisher = {Springer India},
      year = {2014},
      volume = {37},
      number = {5},
      pages = {1047-1051},
      doi = {http://dx.doi.org/10.1007/s12034-014-0043-0}
    }
    
    Priyank Rastogi, Sanjay Kumar, Somnath Bhowmick, Amit Agarwal & Yogesh Singh Chauhan Doping Strategies for Monolayer MoS2 via Surface Adsorption: A Systematic Study 2014 Journal of Physical Chemistry C
    Vol. 118(51), 30309-30314 
    DOI  
    Abstract: Using density functional theory calculations, we have systematically explored the effect of surface adsorption of different atoms on the electronic properties of monolayer molybdenum disulfide (MoS2). We have chosen a few representative members from each group in the periodic table, ranging from alkali metals (group I) to halogens (group VII), and calculated the electronic band structure of the adatom-MoS2 system for the most energetically stable location of the adatom adsorbed on MoS2. The calculated value of charge transfer from the adsorbed adatom to MoS2 and resultant shifting of the Fermi level to the conduction band suggest that the group I (Li, Na, K) and group II metals (Mg, Ca) are the most effective adatoms to enhance the n-type mobile carrier density in MoS2. Our calculation is in good agreement with the experimental observation for K [Nano Lett. 2013, 13, 1991].
    Keywords: ATK, Application, MoS2, adsorption, band structure, charge transfer
    Area: 2dmat, tmd
    BibTeX:
    @article{Rastogi2014,
      author = {Priyank Rastogi and Sanjay Kumar and Somnath Bhowmick and Amit Agarwal and Yogesh Singh Chauhan},
      title = {Doping Strategies for Monolayer MoS2 via Surface Adsorption: A Systematic Study},
      journal = {Journal of Physical Chemistry C},
      year = {2014},
      volume = {118},
      number = {51},
      pages = {30309-30314},
      doi = {http://dx.doi.org/10.1021/jp510662n}
    }
    
    Khurshed A. Shah & Jehangir Rashid Dar Investigation of Doping Effects on Electronic Properties of Two Probe Carbon Nanotube System: A Computational Comparative Study 2014 International Journal of Innovative Research in Science, Engineering and Technology
    Vol. 03(11), 17395-17402 
    DOI  
    Abstract: This paper reports the effect of various dopants on the electronic properties of Zig-Zag (4, 0) semiconducting single walled two probe Carbon Nanotube system using first principle calculations and Non-Equilibrium Green's Function (NEGF) method. The modeled Zig-Zag (4,0) single walled Carbon Nanotube was doped with atoms of elements Tellurium (Te), Antimony (Sb), Arsenic (As) & Chromium (Cr) using Atomistic Tool Kit (version 13.8.1) software and its graphical interface (custom analyzer) Virtual Nanolab. The simulations were carried out in device mode using Density Function Theory (DFT) calculations. The current-voltage (I-V) characteristics & conductance of the four proposed models were studied for comparative study under low-bias conditions. The results show that Arsenic doping has increased the conductance of the model manifold than other doping atoms whereas Chromium doping has showed an amazing property of Negative Differential Resistance (NDR). Hence, we conclude that the proposed model is suitable for use in various CNT based high speed nanoelectronics applications including amplification, oscillation and arithmetic architectures.
    Keywords: Carbon Nanotube device, Non-Equilibrium Green's Function, Doping, Density Function Theory, ATK, Application
    Area: nanotubes
    BibTeX:
    @article{Shah2014,
      author = {Khurshed A. Shah and Jehangir Rashid Dar},
      title = {Investigation of Doping Effects on Electronic Properties of Two Probe Carbon Nanotube System: A Computational Comparative Study},
      journal = {International Journal of Innovative Research in Science, Engineering and Technology},
      publisher = {Ess & Ess Research Publications},
      year = {2014},
      volume = {03},
      number = {11},
      pages = {17395-17402},
      doi = {http://dx.doi.org/10.15680/ijirset.2014.0311044}
    }
    
    Aleksandar Staykov, Motonori Watanabe, Tatsumi Ishihara & Kazunari Yoshizawa Photoswitching of Conductance through Salicylidene Methylamine 2014 Journal of Physical Chemistry C
    Vol. 118(47), 27539-27548 
    DOI  
    Abstract: Photoswitching of conductance through both stable isomers of salicylidene methylamine was investigated using nonequilibrium Green's function method combined with density functional theory. This study demonstrates how the optically induced intramolecular proton transfer between the hydroxyl group and the amino group of salicylidene methylamine can lead to molecular size photodiode with on/off current ratio of 1 order of magnitude. It was further elucidated that the optical switching alone is not sufficient to realize the molecular switch. Of primary importance was found to be the anchoring between the molecule and the metal electrodes. When the anchoring groups were connected to the benzene ring in para-orientation, minimal on/off current ratio was estimated. When the anchoring groups were connected to the benzene ring in meta-orientation, 1 order of magnitude on/off current ratio was calculated. Molecular orbital analysis was successfully employed to elucidate the difference in the photoswitching properties of the meta- and para-anchored isomers of salicylidene methylamine. This study demonstrates the potential application of aromatic Schiff bases as photodiodes in the field of molecular electronics.
    Keywords: ATK, Application, photo switching, salicylidene methyulamine, proton transfer, photodiode, on-off current ratio
    Area: molecular electronics
    BibTeX:
    @article{Staykov2014,
      author = {Aleksandar Staykov and Motonori Watanabe and Tatsumi Ishihara and Kazunari Yoshizawa},
      title = {Photoswitching of Conductance through Salicylidene Methylamine},
      journal = {Journal of Physical Chemistry C},
      year = {2014},
      volume = {118},
      number = {47},
      pages = {27539-27548},
      doi = {http://dx.doi.org/10.1021/jp5081884}
    }
    
    Shi-Hua Tan, Li-Ming Tang & Ke-Qiu Chen Band gap opening in zigzag graphene nanoribbon modulated with magnetic atoms 2014 Current Applied Physics
    Vol. 14(11), 1509 - 1513 
    DOI  
    Abstract: The effects of magnetic atom on the band structure of zigzag-edged graphene nanoribbons are investigated by the density functional theory. The results show that for narrow zigzag-edged graphene nanoribbons, the band gap can be opened duo to the spin-up/spin-down charges being re-enriched on the edge sites. However, for the wide zigzag-edged graphene nanoribbons, a spin-up/spin-down half-metallic property can be observed. Moreover, it is found that the Seebeck coefficients in the narrow zigzag-edged graphene nanoribbons are reversed and enlarged, which provides a way to design novel thermoelectric device.
    Keywords: Electronic band structure of graphene nanoribbon, Density functional theory; Thermoelectric effect, ATK, application
    Area: graphene, nanoribbon, thermo
    BibTeX:
    @article{Tan2014,
      author = {Shi-Hua Tan and Li-Ming Tang and Ke-Qiu Chen},
      title = {Band gap opening in zigzag graphene nanoribbon modulated with magnetic atoms },
      journal = {Current Applied Physics},
      year = {2014},
      volume = {14},
      number = {11},
      pages = {1509 - 1513},
      doi = {http://dx.doi.org/10.1016/j.cap.2014.08.018}
    }
    
    G.P. Tang, Z.H. Zhang, X.Q. Deng, Z.Q. Fan & H.L. Zhu Tuning spin polarization and spin transport of zigzag graphene nanoribbons by line defects 2015 Physical Chemistry Chemical Physics
    Vol. 17, 638-643 
    DOI  
    Abstract: From first-principles methods, the spin-dependent electronic properties of zigzag-edged graphene nanoribbons (ZGNRs) with a line defect (558-defect) are investigated systematically and compared to those of the pristine ZGNR. Results show that the line defect possesses an obvious tuning effect on the spin-polarization of the edge carbon atoms of the defective ZGNRs, and the spin-polarization and spin-transport are sensitive to the position of line defects. The defective ZGNRs can realize a transition from antiferromagnetism (AFM) to ferrimagnetism and ferromagnetism (FM) via changing the position of line defects from the center to the zigzag edge of ZGNRs. More importantly, when the line defect is located at the one edge, the defective ZGNRs exhibit the long-range magnetic ordering at edges with a high Curie temperature up to 276 K, and the defective ZGNR system can generate a high-performance spin-filter effect in the large bias range, 0.0-0.5 V. Such a sensitive modulation for the spin-polarization and spin-transport holds great promise for applications of the graphene-based systems in nano-scale spintronic devices.
    Keywords: ATK, Application, spin transport, graphene nanoribbon, defects, antiferromagnetism, ferrimagnetism, ferromagnetism, Curie temperature, spin filter
    Area: graphene, spin, nanoribbon
    BibTeX:
    @article{Tang2015,
      author = {Tang, G. P. and Zhang, Z. H. and Deng, X. Q. and Fan, Z. Q. and Zhu, H. L.},
      title = {Tuning spin polarization and spin transport of zigzag graphene nanoribbons by line defects},
      journal = {Physical Chemistry Chemical Physics},
      publisher = {The Royal Society of Chemistry},
      year = {2015},
      volume = {17},
      pages = {638-643},
      doi = {http://dx.doi.org/10.1039/C4CP03837A}
    }
    
    Qingyun Wu, Lei Shen, Zhaoqiang Bai, Minggang Zeng, Ming Yang, Zhigao Huang & Yuan Ping Feng Efficient Spin Injection into Graphene through a Tunnel Barrier: Overcoming the Spin-Conductance Mismatch 2014 Phys. Rev. Applied
    Vol. 2, 044008 
    DOI  
    Abstract: Employing first-principles calculations, we investigate the efficiency of spin injection from a ferromagnetic electrode (Ni) into graphene and a possible enhancement by using a barrier between the electrode and graphene. Three types of barriers, h-BN, Cu(111), and graphite, of various thickness (0-3 layers) are considered, and the electrically biased conductance of the Ni/barrier/graphene junction is calculated. It is found that the minority-spin-transport channel of graphene can be strongly suppressed by the insulating h-BN barrier, resulting in a high spin-injection efficiency. On the other hand, the calculated spin-injection efficiencies of Ni/Cu/graphene and Ni/graphite/graphene junctions are low, due to the spin-conductance mismatch. Further examination of the electronic structure of the system reveals that the high spin-injection efficiency in the presence of a tunnel barrier is due to its asymmetric effects on the two spin states of graphene.
    Keywords: Condensed Matter Physics, Graphene, Spintronics, ATK, Application
    Area: graphene, spintronics
    BibTeX:
    @article{Wu2014a,
      author = {Wu, Qingyun and Shen, Lei and Bai, Zhaoqiang and Zeng, Minggang and Yang, Ming and Huang, Zhigao and Feng, Yuan Ping},
      title = {Efficient Spin Injection into Graphene through a Tunnel Barrier: Overcoming the Spin-Conductance Mismatch},
      journal = {Phys. Rev. Applied},
      publisher = {American Physical Society},
      year = {2014},
      volume = {2},
      pages = {044008},
      doi = {http://dx.doi.org/10.1103/PhysRevApplied.2.044008}
    }
    
    Cai-Juan Xia, Kun Gao, De-Hua Zhang, Mao Yang & Fei-Long Feng Conductance switching in single light-sensitive molecular device with carbon nanotube electrodes 2014 Journal of Applied Physics
    Vol. 116(8), 083704 
    DOI  
    Abstract: By applying nonequilibrium Green's function formalism combined first-principles density functional theory, a new mechanism for optical switch of single molecular device with carbon nanotube electrodes is proposed. The molecule comprises the switch can convert between enol and keto isomers upon photoinduced excited state hydrogen transfer in the molecular bridge. Theoretical results show that these two isomers exhibit very different current-voltage characteristics both in armchair and zigzag junction, which can realize the on and off states of the molecular switch. Meantime, the chirality of the single-walled carbon nanotube (SWCNT) electrodes strongly affects the switching characteristics of the molecular junctions. The maximum value of on-off ratio can reach 72 at 1.6 V for the switch with zigzag SWCNT electrodes, suggesting potential applications of this junction in future design of light-driven molecular switches.
    Keywords: Electrodes, Carbon nanotubes, Negative resistance, Density functional theory, Fermi levels, ATK, Application
    Area: molecular electronics
    BibTeX:
    @article{Xia2014,
      author = {Xia, Cai-Juan and Gao, Kun and Zhang, De-Hua and Yang, Mao and Feng, Fei-Long},
      title = {Conductance switching in single light-sensitive molecular device with carbon nanotube electrodes},
      journal = {Journal of Applied Physics},
      year = {2014},
      volume = {116},
      number = {8},
      pages = {083704},
      doi = {http://dx.doi.org/10.1063/1.4894144}
    }
    
    Yipeng An, Kedong Wang, Guangrui Jia, Tianxing Wang, Zhaoyong Jiao, Zhaoming Fu, Xingli Chu, Guoliang Xu & Chuanlu Yang Intrinsic negative differential resistance characteristics in zigzag boron nitride nanoribbons 2014 RSC Advances
    Vol. 4, 46934-46939 
    DOI  
    Abstract: We investigate the charge transport properties of zigzag boron nitride nanoribbons (ZBNNRs) with various hydrogen passivations by employing density functional theory (DFT) combined with the non-equilibrium Green's function (NEGF) formalism. The calculated results reveal that the ZBNNR-based devices exhibit negative differential resistance (NDR) characteristics except those models whose both edges are passivated, due to the mechanism in which the overlap of bands near the Fermi level between the left and right electrodes gets smaller or disappears under a high bias. The NDR characteristics of the perfect ZBNNRs with one or two bare edges are weakly dependent on their widths. This is one intrinsic NDR characteristic of the ZBNNR-based devices, including some defective structures. The intuitive electronic current channels are plotted and analyzed to better understand the charge transport mechanisms. Our results suggest that the ZBNNR-based structures could be favorable candidates for preparing nanoscale NDR devices.
    Keywords: ATK, Application, negative differential resistance, boron nitride BN, nanoribbon
    Area: 2dmat
    BibTeX:
    @article{An2014a,
      author = {An, Yipeng and Wang, Kedong and Jia, Guangrui and Wang, Tianxing and Jiao, Zhaoyong and Fu, Zhaoming and Chu, Xingli and Xu, Guoliang and Yang, Chuanlu},
      title = {Intrinsic negative differential resistance characteristics in zigzag boron nitride nanoribbons},
      journal = {RSC Advances},
      publisher = {The Royal Society of Chemistry},
      year = {2014},
      volume = {4},
      pages = {46934-46939},
      doi = {http://dx.doi.org/10.1039/C4RA08257E}
    }
    
    S. Barzilai, F. Tavazza & L.E. Levine Sensitivity of gold nano-conductors to voids, substitutions, and electric field: ab initio results 2015 Journal of Materials Science
    Vol. 50(1), 412-419 
    DOI  
    Abstract: Gold nanowires are good candidates for nano-electronics devices. A previous study has shown that the beryllium-terminated BeO (0001) surface may be a useful platform for supporting gold nano-conductors, since it preserves the nano wire configuration and does not restrict its conductivity. Here, we used ab initio simulations to determine the sensitivity of potential gold nano-conductors to the presence of point defects, O2 substitutions and to an applied perpendicular electric field, as in field effect transistors. We found that the presence of the point defects causes only small changes in the atomic bond lengths of the NW, does not alter the NW configuration, but may affect the overall conductivity. Single or double voids on the same channel reduce the conductance by 28 % at most, but when the voids arrange in a way that only one channel remains for conductance, it reduces by factor of two to ~1 G0 (G0 = 2e 2/h). The presence of a single O2 molecule as a substitution reduces the electron availability in the neighboring Au atoms, in most cases reducing the conductance. The perpendicular electric field, which is typical for field effect transistors, affects the electron density distribution, shifts and changes the conductance spectra profile, but does not decrease the conductivity.
    Keywords: ATK, Application, gold, Au, nano conductor, nanowires
    Area: nanowires
    BibTeX:
    @article{Barzilai2015,
      author = {Barzilai, S. and Tavazza, F. and Levine, L.E.},
      title = {Sensitivity of gold nano-conductors to voids, substitutions, and electric field: ab initio results},
      journal = {Journal of Materials Science},
      publisher = {Springer US},
      year = {2015},
      volume = {50},
      number = {1},
      pages = {412-419},
      doi = {http://dx.doi.org/10.1007/s10853-014-8600-x}
    }
    
    M. Chakraverty & H.M. Kittur Microstructure processing and micromagnetic simulations of magnetic tunnel junction based low power magnetic memories 2014 Emerging Research Areas: Magnetics, Machines and Drives (AICERA/iCMMD), 2014 Annual International Conference on, 1-6  DOI  
    Abstract: Magnetoresistive memory (MRAM) is one of the forerunners of the nanotechnology enabled memories lined to replace the traditional memories like Flash, DRAM and SRAM. MRAMs are based on the phenomenon of spin dependent tunneling in magnetic tunnel junctions (MTJs). It stores data in the magnetization of a magnetic layer as opposed to electrical charge in conventional RAMs. Yet the read-out of MRAM is electrical. It is claimed to offer something close to the speed of SRAM, with a density approaching that of single-transistor DRAM and the ability to store information when power is removed, like flash memory or EEPROM. This paper works out the microstructure processing steps in the fabrication of an MTJ based MRAM cell in two distinct versions. The technicalities of the two MTJ based MRAM cell configurations have been discussed in this paper. The I-V characteristics and TMR ratios of the widely investigated Fe/MgO/Fe magnetic tunnel junction have also been evaluated using first principle LSDA band-structure calculations. Micro magnetic simulations of the MTJ demonstrate the magnetic switching in the two ferromagnetic layers. The resulting hysteresis loop has been presented at the end of the paper.
    Keywords: MRAM devices;iron;low-power electronics;magnesium compounds;magnetic tunnelling;magnetisation;microfabrication;Fe-MgO-Fe;I-V characteristics;MTJ based MRAM cell;TMR ratios;ferromagnetic layers;first principle LSDA band-structure calculations;hysteresis loop;magnetic switching;magnetic tunnel junctions;magnetization;magnetoresistive memory;micro magnetic simulations;microstructure processing steps;nanotechnology enabled memories;spin dependent tunneling;Copper;Iron;Magnetic fields;Magnetic tunneling;Magnetization;Transistors;Tunneling magnetoresistance;DRAM;EEPROM;Magnetoresistive RAM;SRAM;flash memory;magnetic tunnel junction;spin dependent tunneling;tunnel magnetoresistance, ATK, Application
    Area: semi, spin, nvm
    BibTeX:
    @inproceedings{Chakraverty2014a,
      author = {Chakraverty, M. and Kittur, H.M.},
      title = {Microstructure processing and micromagnetic simulations of magnetic tunnel junction based low power magnetic memories},
      booktitle = {Emerging Research Areas: Magnetics, Machines and Drives (AICERA/iCMMD), 2014 Annual International Conference on},
      year = {2014},
      pages = {1-6},
      doi = {http://dx.doi.org/10.1109/AICERA.2014.6908165}
    }
    
    Bahniman Ghosh & Aayush Gupta EFFECT OF NANORIBBON WIDTH AND STRAIN ON THE ELECTRONIC PROPERTIES OF THE WS2 NANORIBBON 2014 Journal of Electron Devices
    Vol. 20, 1746-1754 
    URL 
    Abstract: Materials of the general form MX2 (transition metal dichalcogenides) have generated a lot of interest recently. They can form nanoribbons like graphene and such nanoribbons have versatile electronic structures and can be metallic or semiconducting by changing the edges of the ribbon. The electronic properties of such materials are not fully understood till now. In this paper we investigate one such material, Tungstenite (WS2). We investigate the band-structure of the zigzag and the armchair nanoribbon. We observe the direct bandgap in the nanoribbons as opposed to indirect bandgap in the bulk material. Also by changing the edge orientation of the nanoribbon from armchair to zigzag, the properties change considerably with zigzag as metallic and armchair as semiconducting. Further we investigate the effect of increasing the ribbon width and the effect of uniaxial and biaxial strain on the nanoribbon.
    Keywords: ATK, Application, nanoribbon, electronic properties, WS2
    Area: 2dmat, tmd
    BibTeX:
    @article{Ghosh2014,
      author = {Bahniman Ghosh and Aayush Gupta},
      title = {EFFECT OF NANORIBBON WIDTH AND STRAIN ON THE ELECTRONIC PROPERTIES OF THE WS2 NANORIBBON},
      journal = {Journal of Electron Devices},
      year = {2014},
      volume = {20},
      pages = {1746-1754},
      url = {http://jeldev.org/20_Ghosh.pdf}
    }
    
    Magdalena Huefner, Ram Krishna Ghosh, Eugene Freeman, Nikhil Shukla, Hanjong Paik, Darrell G. Schlom & Suman Datta Hubbard Gap Modulation in Vanadium Dioxide Nanoscale Tunnel Junctions 2014 Nano Letters
    Vol. 14(11), 6115-6120 
    DOI  
    Abstract: We locally investigate the electronic transport through individual tunnel junctions containing a 10 nm thin film of vanadium dioxide (VO2) across its thermally induced phase transition. The insulator-to-metal phase transition in the VO2 film collapses the Hubbard gap (experimentally determined to be 0.4 +- 0.07 V), leading to several orders of magnitude change in tunnel conductance. We quantitatively evaluate underlying transport mechanisms via theoretical quantum mechanical transport calculations which show excellent agreement with the experimental results.
    Keywords: Atomic force microscopy, metal-insulator transition, vanadium dioxide, density functional theory, non-equilibrium Green's function, tunnel junction, ATK, Application
    Area: semi
    BibTeX:
    @article{Huefner2014,
      author = {Magdalena Huefner and Ram Krishna Ghosh and Eugene Freeman and Nikhil Shukla and Hanjong Paik and Darrell G. Schlom and Suman Datta},
      title = {Hubbard Gap Modulation in Vanadium Dioxide Nanoscale Tunnel Junctions},
      journal = {Nano Letters},
      year = {2014},
      volume = {14},
      number = {11},
      pages = {6115-6120},
      note = {PMID: 25268467},
      doi = {http://dx.doi.org/10.1021/nl502065b}
    }
    
    Young I. Jhon, Kyung S. Min, G.Y. Yeom & Young Min Jhon Understanding time-resolved processes in atomic-layer etching of ultra-thin Al2O3 film using BCl3 and Ar neutral beam 2014 Applied Physics Letters
    Vol. 105(9), 093104 
    DOI  
    Abstract: We scrutinize time-resolved processes occurring in atomic-layer etching (ALET) of ultra-thin Al 2O3 film using BCl3 gas and Ar neutral beam by employing density functional theory calculations and experimental measurements. BCl3 gas is found to be preferentially chemisorbed on Al 2O3(100) in trans form with the surface atoms creating O-B and Al-Cl contacts. We disclose that the most likely sequence of etching events involves dominant detachment of Al-associated moieties at early etching stages in good agreement with our concurrent experiments on tracking Al 2O3 surface compositional variations during Ar bombardment. In this etching regime, we find that ALET requires half the maximum reaction energy of conventional plasma etching, which greatly increases if the etching sequence changes.
    Keywords: Ozone, Plasma etching, Aluminium, Adsorption, Atom surface collisions, ATK, Application
    Area: materials
    BibTeX:
    @article{Jhon2014,
      author = {Jhon, Young I. and Min, Kyung S. and Yeom, G. Y. and Jhon, Young Min},
      title = {Understanding time-resolved processes in atomic-layer etching of ultra-thin Al2O3 film using BCl3 and Ar neutral beam},
      journal = {Applied Physics Letters},
      year = {2014},
      volume = {105},
      number = {9},
      pages = {093104},
      doi = {http://dx.doi.org/10.1063/1.4894523}
    }
    
    Jianming Jia, Xiaoqin Feng & Guibin Chen Electromechanical properties of a zigzag ZnO nanotube under local torsion 2013 Journal of Nanoparticle Research
    Vol. 15(12), 2145 
    DOI  
    Abstract: The electromechanical response of a single-walled zigzag ZnO nanotube under local torsion has been investigated using the density functional theory in combination with the nonequilibrium Green's function method. Our results show that local torsional deformation can cause significant changes of the structural and electrical properties of the semiconducting ZnO nanotube. In the course of twisting, the ZnO nanotube undergoes the structural evolution of elastic and plastic deformation until complete failure, while the transport spectrum and the current-voltage characteristic also depend strongly on the applied torsion. The present results reveal the role of local torsion in tuning the properties of ZnO nanotube, which may prove useful for the design and implementation of one-dimensional ZnO nanostructures in nanoelectromechanical devices.
    Keywords: ZnO nanotube; Electromechanical property; Local torsion; First-principles calculation; ATK, Application
    Area: nanotubes
    BibTeX:
    @article{Jia2013a,
      author = {Jia, Jianming and Feng, Xiaoqin and Chen, Guibin},
      title = {Electromechanical properties of a zigzag ZnO nanotube under local torsion},
      journal = {Journal of Nanoparticle Research},
      publisher = {Springer Netherlands},
      year = {2013},
      volume = {15},
      number = {12},
      pages = {2145},
      doi = {http://dx.doi.org/10.1007/s11051-013-2145-9}
    }
    
    J. Li, Z.H. Zhang, M. Qiu, C. Yuan, X.Q. Deng, Z.Q. Fan, G.P. Tang & B. Liang High-performance current rectification in a molecular device with doped graphene electrodes 2014 Carbon
    Vol. 80, 575 - 582 
    DOI  
    Abstract: To achieve an excellent rectification for molecular rectifiers has been an unmet goal to date. Here, we report calculated results on high-performance molecular rectifiers, where two semi-infinite graphene electrodes are periodically doped with boron and nitrogen atoms, respectively. It is surprising to find that there exists a particular coupling selection for energy bands of electrodes to the central molecule and unique bias-polarity-dependent band matching relations between two electrodes, leading to an unexpectedly high rectification ratio (>109) in a large bias region. This is a much higher value than that for macroscopic p-n junction diodes (105-107), and typical behaviors for conventional diodes are also clearly observed. The robust rectifications are further tested by varying the length and type of molecules, doping concentrations, and width of electrodes.
    Keywords: ATK, Application, rectification, doped graphene
    Area: graphene
    BibTeX:
    @article{Li2014a,
      author = {J. Li and Z.H. Zhang and M. Qiu and C. Yuan and X.Q. Deng and Z.Q. Fan and G.P. Tang and B. Liang},
      title = {High-performance current rectification in a molecular device with doped graphene electrodes },
      journal = {Carbon},
      year = {2014},
      volume = {80},
      pages = {575 - 582},
      doi = {http://dx.doi.org/10.1016/j.carbon.2014.08.098}
    }
    
    Silvio Osella, Paolo Samorì & Jerome Cornil Photoswitching Azobenzene Derivatives in Single Molecule Junctions: A Theoretical Insight into the I/V Characteristics 2014 The Journal of Physical Chemistry C
    Vol. 118(32), 18721-18729 
    DOI  
    Abstract: The I/V characteristics of several photoswitching azobenzene derivatives connected to two gold electrodes to form single-molecule junctions are investigated within the nonequilibrium Green's function formalism coupled to density functional theory. We focus here on the changes in the I/V characteristics as a function of the length and degree of fluorination of the conjugated backbones as well as different coupling strength at the electrodes (chemisorption versus physisorption) upon trans/cis isomerization. The calculations illustrate that the conductance is larger for the trans isomer when the molecule is chemisorbed at both electrodes. However, a larger conduction for the cis isomer is found in the presence of a physisorbed contact at one electrode for specific geometries of the isomer in the junction, in full consistency with the apparent discrepancies observed among experimental measurements. The I/V curves are fully rationalized by analyzing the evolution under bias of the shape of the transmitting molecular orbitals.
    Keywords: ATK, Application, azobenzene, photoswitching
    Area: molecular electronics
    BibTeX:
    @article{Osella2014a,
      author = {Osella, Silvio and Samorì, Paolo and Cornil, Jerome},
      title = {Photoswitching Azobenzene Derivatives in Single Molecule Junctions: A Theoretical Insight into the I/V Characteristics},
      journal = {The Journal of Physical Chemistry C},
      year = {2014},
      volume = {118},
      number = {32},
      pages = {18721-18729},
      doi = {http://dx.doi.org/10.1021/jp504582a}
    }
    
    Sweta Parashar, Pankaj Srivastava, Manisha Pattanaik & Sandeep Kumar Jain Electron transport in asymmetric biphenyl molecular junctions: effects of conformation and molecule-electrode distance 2014 European Physical Journal B
    Vol. 87(9), 220 
    DOI  
    Abstract: On the basis of ab-initio calculations, we predict the effect of conformation and molecule-electrode distance on transport properties of asymmetric molecular junctions for different electrode materials M (M = Au, Ag, Cu, and Pt). The asymmetry in these junctions is created by connecting one end of the biphenyl molecule to conjugated double thiol (model A) and single thiol (model B) groups, while the other end to Cu atom. A variety of phenomena viz. rectification, negative differential resistance (NDR), switching has been observed that can be controlled by tailoring the interface state properties through molecular conformation and molecule-electrode distance for various M. These properties are further analyzed by calculating transmission spectra, molecular orbitals, and orbital energy. It is found that Cu electrode shows significantly enhanced rectifying performance with change in torsion angles, as well as with increase in molecule-electrode distances than Au and Ag electrodes. Moreover, Pt electrode manifests distinctive multifunctional behavior combining switch, diode, and NDR. Thus, the Pt electrode is suggested to be a good potential candidate for a novel multifunctional electronic device. Our findings are compared with available experimental and theoretical results.
    Keywords: Mesoscopic and Nanoscale systems, ATK, Application, biphenyl
    Area: molecular electronics
    BibTeX:
    @article{Parashar2014a,
      author = {Parashar, Sweta and Srivastava, Pankaj and Pattanaik, Manisha and Jain, Sandeep Kumar},
      title = {Electron transport in asymmetric biphenyl molecular junctions: effects of conformation and molecule-electrode distance},
      journal = {European Physical Journal B},
      publisher = {Springer Berlin Heidelberg},
      year = {2014},
      volume = {87},
      number = {9},
      pages = {220},
      doi = {http://dx.doi.org/10.1140/epjb/e2014-50133-2}
    }
    
    Hari P. Paudel The effect of electron-hole pairs in semiconductor and topological insulator nanostructures on plasmon resonances and photon polarizations 2014 School: University of Central Florida  URL 
    Abstract: The generation of electron-hole pairs in materials has great importance. In direct bandgap semiconductor materials, the mechanism of radiative recombination of electronhole pairs leads to the emission of photons, which is the basis of Light Emitting Diodes (LEDs). The excitation of electron-hole pairs by absorption of photons is the active process in photodiodes, solar cells, and other semiconductor photodetector devices. In optoelectronic devices such as optical switches which are based on transmission and reflection of the photons, electron-hole pairs excitation is a key for the device performance. Diodes and transistors are also great discoveries in electronics which rely on the generation and recombination of electron-hole pairs at p-n junctions. In three-dimensional topological insulators (3D TIs) materials nanostructures excitation of electron-hole pairs can be utilized for the quantum memory, quantum information and quantum teleportation. In two-dimensional (2D) layered materials like graphene, MoS2, MoSe2, WS2 and WSe2 generation and recombination of electron hole pairs is main process at p-n junctions, infrared detectors and sensors. This PhD thesis is concerned with the physics of different types of electron-hole pairs in various materials, such as wide-bandgap semiconductors, 3D topological insulators, and plasmonic excitations in metallic nanostructures. The materials of interest are wide bandgap semiconductors such as TiO2 , 3D TIs such as Pb1-xSnxTe and the 2D layered materials such as MoS2 and MoO3. We study the electronic and optical properties in bulk and nanostructures and find applications in the area of semiclassical and quantum information processing. One of the interesting applications we focus in this thesis is shift in surface plasmon resonance due to reduction in index of refraction of surrounding dielectric environment which in turns shifts the wavelength of surface plasmon resonance up to 125 nm for carrier density of 1022/cm3. Employing this effect, we present a model of a light controlled plasmon switching using a hybrid metal-dielectric heterostructures. In 3D TIs nanostructures, the time reversible spin partners in the valence and conduction band can be coupled by a left and a right handed circular polarization of the light. Such coupling of light with electron-hole pair polarization provides an unique opportunity to utilize 3D TIs in quantum information processing and spintronics devices. We present a model of a 3D TI quantum dot made of spherical core-bulk heterostructure. When a 3D TI QD is embedded inside a cavity, the single-photon Faraday rotation provides the possibility to implement optically mediated quantum teleportation and quantum information processing with 3D TI QDs, where the qubit is defined by either an electron-hole pair, a single electron spin, or a single hole spin in a 3D TI QD. Due to excellent transport properties in single and multiple layers of 2D layered materials, several efforts have demonstrated the possibility to engineer electronic and optoelectronic devices based on MoS2. In this thesis, we focus on theoretical and experimental study of electrical property and photoluminescence tuning, both in a single-layer of MoS2. We present theoretical analysis of experimental results from the point of view of stability of MoO3 defects in MoS2 single layer and bandstructures calculation. In experiment, the electrical property of a single layer of MoS2 can be tuned from semiconducting to insulating regime via controlled exposure to oxygen plasma. The quenching of photoluminescence of a single sheet of MoS2 has also been observed upon exposure to oxygen plasmas. We calculate the direct to indirect band gap transitions by going from MoS2 single sheet to MoO3 single sheet during the plasma exposure, which is due to the formation of MoO3 rich defect domains inside a MoS2 sheet.
    Keywords: ATK, Application, electron-hole pairs, topological insulator, plasmons
    Area: semi
    BibTeX:
    @phdthesis{Paudel2014,
      author = {Hari P. Paudel},
      title = {The effect of electron-hole pairs in semiconductor and topological insulator nanostructures on plasmon resonances and photon polarizations},
      school = {University of Central Florida},
      year = {2014},
      url = {http://etd.fcla.edu/CF/CFE0005397/HariPaudel_PhD_Thesis.pdf}
    }
    
    Jun Peng, Wu-Xing Zhou & Ke-Qiu Chen High-efficiency spin filtering in salophen-based molecular junctions modulated with different transition metal atoms 2014 Physics Letters A
    Vol. 378(42), 3126 - 3130 
    DOI  
    Abstract: Based on the density functional theory and nonequilibrium Green's function methods, we investigate the spin transport properties of the molecular junctions constructed by a homologous series of 3d transition metal(II) salophens (TM-salophens, TM = Co, Fe, Ni and Mn) sandwiched between two gold electrodes. It is found that among the four molecular junctions only Co-salophen junction can act as an efficient spin filter distinctively. The conductance through Co-salophen molecular junction is dominated by spin-down electrons. The mechanism is proposed for these phenomena.
    Keywords: Spin transport properties, Magnetic molecular junctions, ATK, Application
    Area: molecular electronics, spin
    BibTeX:
    @article{Peng2014a,
      author = {Jun Peng and Wu-Xing Zhou and Ke-Qiu Chen},
      title = {High-efficiency spin filtering in salophen-based molecular junctions modulated with different transition metal atoms},
      journal = {Physics Letters A},
      year = {2014},
      volume = {378},
      number = {42},
      pages = {3126 - 3130},
      doi = {http://dx.doi.org/10.1016/j.physleta.2014.09.015}
    }
    
    Wanzhi Qiu & Efstratios Skafidas Detection of Protein Conformational Changes with Multilayer Graphene Nanopore Sensors 2014 ACS Applied Materials and Interfaces
    Vol. 6(19), 16777-16781 
    DOI  
    Abstract: Detecting conformational change in protein or peptide is imperative in understanding their dynamic function and diagnosing diseases. Existing techniques either rely on ensemble average that lacks the necessary sensitivity or require florescence labeling. Here we propose to discriminate between different protein conformations with multiple layers of graphene nanopore sensors by measuring the effect of protein-produced electrostatic potential (EP) on electric transport. Using conformations of the octapeptide Angiotensin II obtained through molecular dynamics simulations, we show that the EP critically depends on the geometries of constituent atoms and each conformation carries a unique EP signature. We then, using quantum transport simulations, reveal that these characteristic EP profiles cause distinctive modulation to electric charge densities of the graphene nanopores, leading to distinguishable changes in conductivity. Our results open the potential of label-free, single-molecule, and real-time detection of protein conformational changes.
    Keywords: protein conformational change, graphene nanopores, biosensors, electrostatic potential, quantum conductance, ATK, Application
    Area: graphene
    BibTeX:
    @article{Qiu2014a,
      author = {Qiu, Wanzhi and Skafidas, Efstratios},
      title = {Detection of Protein Conformational Changes with Multilayer Graphene Nanopore Sensors},
      journal = {ACS Applied Materials and Interfaces},
      year = {2014},
      volume = {6},
      number = {19},
      pages = {16777-16781},
      note = {PMID: 25185959},
      doi = {http://dx.doi.org/10.1021/am5040279}
    }
    
    Florina Regius, Gnaneshwar.P.V, Arjun Senthil, Moon Paul & Varun Nair Structural, Electronic and Optical Properties of Doped Titanium Nanowire 2014 International Journal of Science and Research
    Vol. 3(9)International Journal of Science and Research (IJSR), 1442-1445 
    URL 
    Abstract: Electronic optical and structural properties of Titanium Nanowire (TiNW) when doped with Al and P atoms are obtained from simulation studies have been reviewed. The band gap, density of states, optical spectrum and Structural property of Titanium Nanowire has been compared when this nanowire is doped with phosphorus and aluminium atoms. We observed that decrease in band gap increases the metallic property of silicon. Total energy is maximum then the structure is least stable. So we can say that total energy is inversely proportional to stability. In density of states, we clearly see the decline in DOS/eV with the increase of doping Al and P atoms. In this paper, we have discussed all the electronic and structural properties.
    Keywords: Band structure, Band gap, Density of States, TiNW, ATK, Application
    Area: nanowires
    BibTeX:
    @article{Regius2014,
      author = {Florina Regius and Gnaneshwar.P.V and Arjun Senthil and Moon Paul and Varun Nair},
      title = {Structural, Electronic and Optical Properties of Doped Titanium Nanowire},
      booktitle = {International Journal of Science and Research (IJSR)},
      journal = {International Journal of Science and Research},
      year = {2014},
      volume = {3},
      number = {9},
      pages = {1442-1445},
      url = {http://www.ijsr.net/archive/v3i9/U0VQMTQ0OA==.pdf}
    }
    
    L.L. Song, X.H. Zheng, H. Hao, J. Lan, X.L. Wang & Z. Zeng Tuning the electron transport properties of boron-nitride nanoribbons with electron and hole doping 2014 RSC Advances
    Vol. 4, 48212-48219 
    DOI  
    Abstract: By first principles calculations based on the density functional theory and nonequilibrium Green's function technique, we have studied the electronic and transport properties of C-doped zigzag-edged boron-nitride nanoribbons (ZBNNRs). Due to the two sub-lattices in boron-nitride nanoribbons (BNNRs), C substitutions at B sites and N sites naturally provide ways for electron doping and hole doping. Different combinations of the C chain substitution schemes are utilized to tune the electron transport of nano junctions constructed with ZBNNRs. It is found that, either substitution for B or N by C, in symmetric doping, the junction always behaves as a good conductor. However, in the asymmetric doping, the performance of the junctions highly depends on the positions of the C chain. When the C atoms are doped at opposite edges on the two sides of the junction, there is no current across the junction although dopings at B site and N site can both transform a BNNR from an insulator into a metal. Interestingly, when the doping sites are moved to the middle of the ribbons, the junctions conduct very well and negative differential resistance (NDR) is observed due to the special alignment of the energy bands of the two leads.
    Keywords: ATK, Application, boron nitride, nanoribbons, doping
    Area: 2dmat
    BibTeX:
    @article{Song2014,
      author = {Song, L. L. and Zheng, X. H. and Hao, H. and Lan, J. and Wang, X. L. and Zeng, Z.},
      title = {Tuning the electron transport properties of boron-nitride nanoribbons with electron and hole doping},
      journal = {RSC Advances},
      publisher = {The Royal Society of Chemistry},
      year = {2014},
      volume = {4},
      pages = {48212-48219},
      doi = {http://dx.doi.org/10.1039/C4RA07769E}
    }
    
    Anurag Srivastava, Kamalpreet Kaur, Ritu Sharma, Priyanka Chauhan, U.S. Sharma & Chetan Pathak Orientation-Dependent Performance Analysis of Benzene/Graphene-Based Single-Electron Transistors 2014 Journal of Electronic Materials
    Vol. 43(9), 3449-3457 
    DOI  
    Abstract: The present paper discusses charge stability and conductance analyses of benzene- and zigzag graphene fragment-based single-electron transistors (SETs) operating in the Coulomb blockade regime. Graphene and benzene are modeled using density functional theory-based ab initio analyses, treating the interaction between graphene/benzene and the SET environment self-consistently. The devices consist of an oriented graphene/benzene island coupled with source and drain electrodes. The charging energy as a function of the external gate potential has been analyzed to verify the dependence of the charge stability and conductance of the oriented SETs on the source/drain bias and gate potential. Comparative analysis of these models shows that the SET with vertically oriented graphene is more stable and has better conductance in comparison with the benzene-based SET.
    Keywords: Single-electron transistor; graphene; benzene; orientation; ab initio; charge stability; conductance, ATK, Application
    Area: graphene
    BibTeX:
    @article{Srivastava2014b,
      author = {Srivastava, Anurag and Kaur, Kamalpreet and Sharma, Ritu and Chauhan, Priyanka and Sharma, U.S. and Pathak, Chetan},
      title = {Orientation-Dependent Performance Analysis of Benzene/Graphene-Based Single-Electron Transistors},
      journal = {Journal of Electronic Materials},
      publisher = {Springer US},
      year = {2014},
      volume = {43},
      number = {9},
      pages = {3449-3457},
      doi = {http://dx.doi.org/10.1007/s11664-014-3272-5}
    }
    
    Xiaojian Tan, Hezhu Shao, Yanwei Wen, Huijun Liu & Guoqiang Liu Three-dimensional hybridized carbon networks for high performance thermoelectric applications 2014 RSC Advances
    Vol. 4, 42234-42239 
    DOI  
    Abstract: Thermoelectric properties of three-dimensional covalently connected carbon networks are investigated by using first-principles calculation, Boltzmann transport theory, and nonequilibrium molecular dynamics simulations. It is found that the electronic transport of such networks exhibit "ballistic transport" behavior, similar to single carbon nanotubes. The thermoelectric performance of network structures is significantly enhanced relative to one-dimensional carbon nanotubes, owing to the high power factor and largely reduced thermal conductivity. The ZT value of carbon network (9,0) at intermediate temperature can be increased to 0.78 by n-type doping with a carrier concentration of 3.9 x 1019 cm-3. Therefore carbon networks are expected to be potential candidates for eco-friendly thermoelectric materials.
    Keywords: ATK, Application, thermoelectrics
    Area: graphene, thermo
    BibTeX:
    @article{Tan2014a,
      author = {Tan, Xiaojian and Shao, Hezhu and Wen, Yanwei and Liu, Huijun and Liu, Guoqiang},
      title = {Three-dimensional hybridized carbon networks for high performance thermoelectric applications},
      journal = {RSC Advances},
      publisher = {The Royal Society of Chemistry},
      year = {2014},
      volume = {4},
      pages = {42234-42239},
      doi = {http://dx.doi.org/10.1039/C4RA06149G}
    }
    
    Ankit Kumar Verma, Bahniman Ghosh, Bhaskar Awadhiya & Tangudu Bharat Kumar Ab-Initio Modeling of Effect of Boron and Phosphorus Doping in CoFe/MgO Magnetic Tunnel Junctions 2014 Journal of Low Power Electronics
    Vol. 10(3), 361-364(4) 
    DOI  
    Abstract: In this work analysis of Boron and Phosphorus doping in CoFe/MgO Magnetic Tunnel Junction has been carried out using first principle calculations. Boron and Phosphorus are doped in CoFe electrode, at electrode barrier interface and in the bulk. In case of Boron doping tunneling magneto-resistance (TMR) of magnetic tunnel junction is reduced to a much lower value when it is doped at electrode barrier interface instead of bulk. However in case of Phosphorus doping TMR is almost same as when Boron atoms are doped in the bulk of electrode. Boron atoms present at interface cause distortion in &delta;1 state symmetry which in turn tempers majority channel conductance. So prevention of Boron doping at interface or doping of Phosphorus atoms could result in the device having much higher value of TMR.
    Keywords: magnetic random access memory (MRAM); magnetic tunnel junction (MTJ); spin dependent generalized gradient approximation (SGGA); spintronics; tunneling magneto-resistance (TMR); ATK, Application
    Area: interfaces, nvm
    BibTeX:
    @article{Verma2014,
      author = {Verma, Ankit Kumar and Ghosh, Bahniman and Awadhiya, Bhaskar and Kumar, Tangudu Bharat},
      title = {Ab-Initio Modeling of Effect of Boron and Phosphorus Doping in CoFe/MgO Magnetic Tunnel Junctions},
      journal = {Journal of Low Power Electronics},
      year = {2014},
      volume = {10},
      number = {3},
      pages = {361-364(4)},
      doi = {http://dx.doi.org/10.1166/jolpe.2014.1349}
    }
    
    Bo Xiao & Satoshi Watanabe Oxygen vacancy effects on an amorphous-TaOx-based resistance switch: a first principles study 2014 Nanoscale
    Vol. 6(17), 10169-10178 
    DOI  
    Abstract: Amorphous TaOx (a-TaOx) based resistance switches have recently demonstrated outstanding performance and are being considered as one of the most promising candidates for next-generation memory cells. However, the origin of the switching mechanism is still under debate, especially on the component of the conduction filament (CF). Since the resistance change of a-TaOx is controlled by the O concentration, we perform a systematic investigation on the evolution of structures and electronic properties of a-TaOx (0.75 < x < 2.85) from first principles. Our results reveal the strong correlation among Ta/O coordination numbers, Ta-Ta/Ta-O bond lengths, and O concentrations in a-TaOx. For a single O vacancy in a-TaO2.5, the Ta-Ta dimer structure is found to be the most stable, and the energy position of its defect state agrees well with experiments. With the decrease of O concentration, Ta atoms tend to merge together and finally form a continuous Ta-rich region in a-TaO0.75, which suggests that not O vacancies, but the Ta-Ta bonding mainly contributes to the CF in a-TaOx based resistance switches. Our molecular dynamics simulation suggests that in the CF, Ta atoms prefer to arrange in a layer structure, and hence the phase transformation to crystalline &alpha;-Ta with interstitial O atoms is proposed. In addition, the calculations on Pt/a-TaOx/Pt heterostructures further confirm the conductive nature of the Ta-Ta bonding in a-TaOx, and also reveal the different conduction types in switching on (metallic contact) and off (electron hopping) states.
    Keywords: ATK, Application, vacancies, defects
    Area: semi, interfaces
    BibTeX:
    @article{Xiao2014a,
      author = {Xiao, Bo and Watanabe, Satoshi},
      title = {Oxygen vacancy effects on an amorphous-TaOx-based resistance switch: a first principles study},
      journal = {Nanoscale},
      publisher = {Royal Society of Chemistry (RSC)},
      year = {2014},
      volume = {6},
      number = {17},
      pages = {10169-10178},
      doi = {http://dx.doi.org/10.1039/c4nr02173h}
    }
    
    Jing Zeng, Ke-Qiu Chen, Liezun Chen, Xiaohui Deng & Zhiping Dai Designing cross-linked carbon nanotubes as perfect spin filter and spin valve 2014 Organic Electronics
    Vol. 15(10), 2561 - 2567 
    DOI  
    Abstract: By applying nonequilibrium Green's functions in combination with density-function theory, the spin-dependent transport properties of cross-linked carbon nanotube spintronic devices are investigated. Our calculations show that the perfect spin filtering effect with the almost 100% spin polarization, and the magnetoresistance effect with a magnetoresistance ratio larger than 10 4 % can be observed in the device. The occurrence of the perfect spin-filtering and magnetoresistance effects in the cross-linked carbon nanotube spintronic device provides the possibility for further improving the integration level of carbon nanotube networks. Moreover, the mechanisms for these interesting phenomena are suggested.
    Keywords: spin filter, spin valve, spin transport, carbon nanotubes, ATK, Application
    Area: spintronics
    BibTeX:
    @article{Zeng2014a,
      author = {Jing Zeng and Ke-Qiu Chen and Liezun Chen and Xiaohui Deng and Zhiping Dai},
      title = {Designing cross-linked carbon nanotubes as perfect spin filter and spin valve},
      journal = {Organic Electronics},
      year = {2014},
      volume = {15},
      number = {10},
      pages = {2561 - 2567},
      doi = {http://dx.doi.org/10.1016/j.orgel.2014.07.013}
    }
    
    A. Zienert, J. Schuster & T. Gessner Metallic carbon nanotubes with metal contacts: electronic structure and transport 2014 Nanotechnology
    Vol. 25(42), 425203 
    DOI  
    Abstract: We study quasi-ballistic electron transport in metallic (6, 0) carbon nanotubes (CNTs) of variable length in contact with Al, Cu, Pd, Pt, Ag, and Au electrodes by using the non-equilibrium Green's function formalism in combination with either density functional theory or self-consistent extended Hückel theory. We find good agreement between both. Visualizing the local device density of states of the systems gives a descriptive link between electronic structure and transport properties. In comparison with bare finite and infinite tubes, we show that the electronic structure of short metallic CNTs is strongly modified by the presence of the metallic electrodes, which leads to pronounced size effects in the conductance. The mean conductances and linear response currents allow a ranking of the metals regarding their ability to form low-Ohmic contacts with the nanotube: Ag <~ Au < Cu << Pt ~~ Pd << Al. These findings are contrasted with similar trends in contact distance, binding energy, calculated work function of the metal surfaces, and various results from literature.
    Keywords: electronic transport, carbon nanotube, contact, Green's function, density functional theory, extended Hückel theory, ATK-SE, Application
    Area: nanotubes
    BibTeX:
    @article{Zienert2014,
      author = {A. Zienert and J. Schuster and T. Gessner},
      title = {Metallic carbon nanotubes with metal contacts: electronic structure and transport},
      journal = {Nanotechnology},
      year = {2014},
      volume = {25},
      number = {42},
      pages = {425203},
      doi = {http://dx.doi.org/10.1088/0957-4484/25/42/425203}
    }
    
    Rui-Li An, Xue-Feng Wang, P. Vasilopoulos, Yu-Shen Liu, An-Bang Chen, Yao-Jun Dong & Ming-Xing Zhai Vacancy Effects on Electric and Thermoelectric Properties of Zigzag Silicene Nanoribbons 2014 The Journal of Physical Chemistry C
    Vol. 118(37), 21339-21346 
    DOI  
    Abstract: We study the crystal reconstruction in the presence of monovacancies (MVs), divacancies (DVs), and linear vacancies (LVs) in a zigzag silicene nanoribbon (ZSiNR) with transversal symmetry. Their influence on the electric and thermoelectric properties is assessed by the density functional theory combined with the nonequilibrium Green's functions. In particular, we focus on the spin resolved conductance, magnetoresistance and current-voltage curves. A 5-atom-ring is formed in MVs, a 5-8-5 ring structure in DVs, and a 8-4-8-4 ring structure in LVs. The linear conductance becomes strongly spin-dependent when the transversal symmetry is broken by vacancies, especially if they are located on the ribbon's edges. The giant magnetoresistance can be smeared by asymmetric vacancies. Single spin negative differential resistance may appear in the presence of LVs and asymmetric MVs or DVs. A strong spin Seebeck effect is expected at room temperature in ZSiNRs with LVs.
    Keywords: ATK, Application, vacancy, thermoelectrics, silicene, nanoribbon
    Area: 2dmat, thermo
    BibTeX:
    @article{An2014,
      author = {An, Rui-Li and Wang, Xue-Feng and Vasilopoulos, P. and Liu, Yu-Shen and Chen, An-Bang and Dong, Yao-Jun and Zhai, Ming-Xing},
      title = {Vacancy Effects on Electric and Thermoelectric Properties of Zigzag Silicene Nanoribbons},
      journal = {The Journal of Physical Chemistry C},
      year = {2014},
      volume = {118},
      number = {37},
      pages = {21339-21346},
      doi = {http://dx.doi.org/10.1021/jp506111a}
    }
    
    Po-Hao Chang, Haiying Liu & Branislav K. Nikolic First-principles versus semi-empirical modeling of global and local electronic transport properties of graphene nanopore-based sensors for DNA sequencing 2014 Journal of Computational Electronics
    Vol. 13(4), 847-856 
    DOI  
    Abstract: Using first-principles quantum transport simulations, based on the nonequilibrium Green function formalism combined with density functional theory (NEGF+DFT), we examine changes in the total and local electronic currents within the plane of graphene nanoribbon with zigzag edges (ZGNR) hosting a nanopore which are induced by inserting a DNA nucleobase into the pore. We find a sizable change of the zero-bias conductance of two-terminal ZGNR + nanopore device after the nucleobase is placed into the most probable position (according to molecular dynamics trajectories) inside the nanopore of a small diameter D=1.2 nm. Although such effect decreases as the nanopore size is increased to D=1.7 nm, the contrast between currents in ZGNR + nanopore and ZGNR + nanopore + nucleobase systems can be enhanced by applying a small bias voltage Vb<0.1 V. This is explained microscopically as being due to DNA nucleobase-induced modification of spatial profile of local current density around the edges of ZGNR. We repeat the same analysis using NEGF combined with self-consistent charge density functional tight-binding (NEGF+SCC-DFTB) or self-consistent extended Huckel (NEGF+SC-EH) semi-empirical methodologies. The large discrepancy we find between the results obtained from NEGF+DFT vs. those obtained from NEGF+SCC-DFTB or NEGF+SC-EH approaches could be of great importance when selecting proper computational algorithms for in silico design of optimal nanoelectronic sensors for rapid DNA sequencing.
    Keywords: Graphene nanoribbons; Nanopores; DNA sequencing; First-principles quantum transport, ATK, application
    Area: graphene
    BibTeX:
    @article{Chang2014,
      author = {Chang, Po-Hao and Liu, Haiying and Nikolic, Branislav K.},
      title = {First-principles versus semi-empirical modeling of global and local electronic transport properties of graphene nanopore-based sensors for DNA sequencing},
      journal = {Journal of Computational Electronics},
      publisher = {Springer US},
      year = {2014},
      volume = {13},
      number = {4},
      pages = {847-856},
      doi = {http://dx.doi.org/10.1007/s10825-014-0614-8}
    }
    
    Bin Cui, Wenkai Zhao, Hui Wang, Jingfen Zhao, He Zhao, Dongmei Li, Xiaohui Jiang, Peng Zhao & Desheng Liu Effect of geometrical torsion on the rectification properties of diblock conjugated molecular diodes 2014 Journal of Applied Physics
    Vol. 116(7), 073701 
    DOI  
    Abstract: We model several Au/conjugated molecule/Au junctions in the presence of molecular geometrical torsions. A rectification ratio of around 10 in the twisty diphenyldipyrimidinyl system is obtained, which is in good agreement with experiment. Deeper insight into the rectification mechanism of the conjugated molecular diodes is presented on the basis of simulations in a set of simpler but similar junctions. The rectification effect (the ratio) is significantly improved with increasing the molecular twist, while the conductance is reduced accordingly. Our results suggest that the rectification can be enhanced by the geometrical-torsion-induced reduction in the conjugation length of organic molecules.
    Keywords: ATK, Application, torsion, rectification, molecular diode, Au, gold
    Area: molecular electronics
    BibTeX:
    @article{Cui2014a,
      author = {Cui, Bin and Zhao, Wenkai and Wang, Hui and Zhao, Jingfen and Zhao, He and Li, Dongmei and Jiang, Xiaohui and Zhao, Peng and Liu, Desheng},
      title = {Effect of geometrical torsion on the rectification properties of diblock conjugated molecular diodes},
      journal = {Journal of Applied Physics},
      year = {2014},
      volume = {116},
      number = {7},
      pages = {073701},
      doi = {http://dx.doi.org/10.1063/1.4893365}
    }
    
    Yao-Jun Dong, Xue-Feng Wang, Shuo-Wang Yang & Xue-Mei Wu High performance current and spin diode of atomic carbon chain between transversely symmetric ribbon electrodes 2014 Scientific Reports
    Vol. 4, 6157 
    DOI  
    Abstract: We demonstrate that giant current and high spin rectification ratios can be achieved in atomic carbon chain devices connected between two symmetric ferromagnetic zigzag-graphene-nanoribbon electrodes. The spin dependent transport simulation is carried out by density functional theory combined with the non-equilibrium Green's function method. It is found that the transverse symmetries of the electronic wave functions in the nanoribbons and the carbon chain are critical to the spin transport modes. In the parallel magnetization configuration of two electrodes, pure spin current is observed in both linear and nonlinear regions. However, in the antiparallel configuration, the spin-up (down) current is prohibited under the positive (negative) voltage bias, which results in a spin rectification ratio of order 104. When edge carbon atoms are substituted with boron atoms to suppress the edge magnetization in one of the electrodes, we obtain a diode with current rectification ratio over 106.
    Keywords: ATK, Application, spintronics, diode, carbon chain, nanoribbon
    Area: spintronics
    BibTeX:
    @article{Dong2014a,
      author = {Dong, Yao-Jun and Wang, Xue-Feng and Yang, Shuo-Wang and Wu, Xue-Mei},
      title = {High performance current and spin diode of atomic carbon chain between transversely symmetric ribbon electrodes},
      journal = {Scientific Reports},
      publisher = {Nature Publishing Group},
      year = {2014},
      volume = {4},
      pages = {6157},
      doi = {http://dx.doi.org/10.1038/srep06157}
    }
    
    N. Liu, G.Y. Gao, S.C. Zhu, Y. Ni, S.L. Wang, J.B. Liu & K.L. Yao Carbon doping induced peculiar transport properties of boron nitride nanoribbons p-n junctions 2014 Journal of Applied Physics
    Vol. 116(2), 023708 
    DOI  
    Abstract: By applying nonequilibrium Green's function combined with density functional theory, we investigate the electronic transport properties of carbon-doped p-n nanojunction based on hexagonal boron nitride armchair nanoribbons. The calculated I-V curves show that both the center and edge doping systems present obvious negative differential resistance (NDR) behavior and excellent rectifying effect. At low positive bias, the edge doping systems possess better NDR performance with larger peak-to-valley ratio (~105), while at negative bias, the obtained peak-to-valley ratio for both of the edge and center doping systems can reach the order of 107. Meanwhile, center doping systems present better rectifying performance than the edge doping ones, and giant rectification ratio up to 106 can be obtained in a wide bias range. These outstanding transport properties are explained by the evolution of the transmission spectra and band structures with applied bias, together with molecular projected self-consistent Hamiltonian eigenvalues and eigenstates.
    Keywords: ATK, Application, carbon doping, boron nitride, BN, nanoribbon
    Area: graphene, nanoribbons
    BibTeX:
    @article{Liu2014c,
      author = {Liu, N. and Gao, G. Y. and Zhu, S. C. and Ni, Y. and Wang, S. L. and Liu, J. B. and Yao, K. L.},
      title = {Carbon doping induced peculiar transport properties of boron nitride nanoribbons p-n junctions},
      journal = {Journal of Applied Physics},
      year = {2014},
      volume = {116},
      number = {2},
      pages = {023708},
      doi = {http://dx.doi.org/10.1063/1.4890225}
    }
    
    Wu Liu, Kaiwang Zhang, Ru-Zhi Wang, JianXin Zhong & Li-Min Liu Modulation of the electron transport properties in graphene nanoribbons doped with BN chains 2014 AIP Advances
    Vol. 4(6), 067123 
    DOI  
    Abstract: Using density-functional theory and the non-equilibrium Green's function method, the electron transport properties of zigzag graphene nanoribbons (ZGNRs) doped with BN chains are studied by systematically calculating the energy band structure, density of states and the transmission spectra for the systems. The BN chains destroyed the electronic transport properties of the ZGNRs, and an energy gap appeared for the ZGNRs, and displayed variations from a metal to a wide-gap semiconductor. With an increase in the number of BN chains, the band gap increased gradually in the band structure and the transmission coefficient decreased near the Fermi surface. Additionally, the doping position had a significant effect on the electronic properties of the ZGNRs.
    Keywords: ATK, Application, electron transport, graphene, nanoribbon, BN, boron nitride
    Area: graphene
    BibTeX:
    @article{Liu2014e,
      author = {Liu, Wu and Zhang, Kaiwang and Wang, Ru-Zhi and Zhong, JianXin and Liu, Li-Min},
      title = {Modulation of the electron transport properties in graphene nanoribbons doped with BN chains},
      journal = {AIP Advances},
      year = {2014},
      volume = {4},
      number = {6},
      pages = {067123},
      doi = {http://dx.doi.org/10.1063/1.4883236}
    }
    
    Y. Min, J.H. Fang, C.G. Zhong, Z.C. Dong, J.F. Li, K.L. Yao & L.P. Zhou Contact transparency inducing low bias negative differential resistance in two capped carbon nanotubes sandwiching sigma barrier 2015 Applied Physics A
    Vol. 118(1), 367-371 
    DOI  
    Abstract: A first-principles study of the transport properties of two capped (5, 5) carbon nanotubes sandwiching sigma barrier is reported. Contact transparency at zero bias is obtained. Strong negative differential resistance effect with large peak-to-valley ratio of 1,124 % is present under very low bias, which may promise the potential applications in nano-electronic devices with low power dissipation in the future.
    Keywords: ATK, Application, contact, negative differenaial resistance, carbon nanotube
    Area: nanotubes
    BibTeX:
    @article{Min2015,
      author = {Min, Y. and Fang, J.H. and Zhong, C.G. and Dong, Z.C. and Li, J.F. and Yao, K.L. and Zhou, L.P.},
      title = {Contact transparency inducing low bias negative differential resistance in two capped carbon nanotubes sandwiching sigma barrier},
      journal = {Applied Physics A},
      publisher = {Springer Berlin Heidelberg},
      year = {2015},
      volume = {118},
      number = {1},
      pages = {367-371},
      doi = {http://dx.doi.org/10.1007/s00339-014-8743-2}
    }
    
    Yuanyuan Pan, Yangyang Wang, Lu Wang, Hongxia Zhong, Ruge Quhe, Zeyuan Ni, Meng Ye, Wai-Ning Mei, Junjie Shi, Wanlin Guo, Jinbo Yang & Jing Lu Graphdiyne-metal contacts and graphdiyne transistors 2015 Nanoscale
    Vol. 7, 2116-2127 
    DOI URL 
    Abstract: Graphdiyne was prepared on a metal surface, and the preparation of devices using it inevitably involves its contact with metals. Using density functional theory with dispersion correction, we systematically studied, for the first time, the interfacial properties of graphdiyne that is in contact with a series of metals (Al, Ag, Cu, Au, Ir, Pt, Ni, and Pd). Graphdiyne forms an n-type Ohmic or quasi-Ohmic contact with Al, Ag, and Cu, while it forms a Schottky contact with Pd, Au, Pt, Ni, and Ir (at the source/drain-channel interface), with high Schottky barrier heights of 0.21, 0.46 (n-type), 0.30, 0.41, and 0.46 (p-type) eV, respectively. A graphdiyne field effect transistor (FET) with Al electrodes was simulated using quantum transport calculations. This device exhibits an on-off ratio up to 104 and a very large on-state current of 1.3 [times] 104 mA mm-1 in a 10 nm channel length. Thus, a new prospect has opened up for graphdiyne in high performance nanoscale devices.
    Keywords: ATK, Application, graphdyine
    Area: graphene
    BibTeX:
    @article{Pan2015,
      author = {Pan, Yuanyuan and Wang, Yangyang and Wang, Lu and Zhong, Hongxia and Quhe, Ruge and Ni, Zeyuan and Ye, Meng and Mei, Wai-Ning and Shi, Junjie and Guo, Wanlin and Yang, Jinbo and Lu, Jing},
      title = {Graphdiyne-metal contacts and graphdiyne transistors},
      journal = {Nanoscale},
      year = {2015},
      volume = {7},
      pages = {2116-2127},
      url = {http://arxiv.org/abs/1408.3480},
      doi = {http://dx.doi.org/10.1039/c4nr06541g}
    }
    
    Dipankar Saha, Amretashis Sengupta, Sitangshu Bhattacharya & Santanu Mahapatra Impact of Stone-Wales and lattice vacancy defects on the electro-thermal transport of the free standing structure of metallic ZGNR 2014 Journal of Computational Electronics
    Vol. 13(4), 862-871 
    DOI  
    Abstract: We report the effect of topological as well as lattice vacancy defects on the electro-thermal transport properties of the metallic zigzag graphene nano ribbons at their ballistic limit. We employ the density function theory-Non equilibrium green's function combination to calculate the transmission details. We then present an elaborated study considering the variation in the electrical current and the heat current transport with the change in temperature as well as the voltage gradient across the nano ribbons. The comparative analysis shows, that in the case of topological defects, such as the Stone-Wales defect, the electrical current transport is minimum. Besides, for the voltage gradient of 0.5 Volt and the temperature gradient of 300 K, the heat current transport reduces by ~62% and ~50% for the cases of Stones-Wales defect and lattice vacancy defect respectively, compared to that of the perfect one.
    Keywords: ZGNR; Stone-Wales defect; Lattice vacancy defect; Metallic; Electrical current; Thermal transport, DFT, ATK, Application
    Area: graphene, thermo
    BibTeX:
    @article{Saha2014,
      author = {Saha, Dipankar and Sengupta, Amretashis and Bhattacharya, Sitangshu and Mahapatra, Santanu},
      title = {Impact of Stone-Wales and lattice vacancy defects on the electro-thermal transport of the free standing structure of metallic ZGNR},
      journal = {Journal of Computational Electronics},
      publisher = {Springer US},
      year = {2014},
      volume = {13},
      number = {4},
      pages = {862-871},
      doi = {http://dx.doi.org/10.1007/s10825-014-0601-0}
    }
    
    J.V.N. Sarma, Rajib Chowdhury & R. Jayaganthan Graphyne-based single electron transistor: ab initio analysis 2014 Nano
    Vol. 09(03), 1450032 
    DOI  
    Abstract: The application of graphyne for a single-electron transistor (SET) that is operating in the Coulomb blockade regime is investigated in the first principles framework. Density functional theory modeling for graphyne has been used and the device environment has been described by a continuum model. The interaction between graphyne and the SET environment is treated with self-consistent Poisson equations. The charging energy as a function of gate voltage thus calculated has been used to obtain the charge stability diagram for the present system. The effect of electrode separation and the position of the molecule with respect to the dielectric on the gate coupling have been studied further. As compared with the previously studied systems on this line, graphyne has been observed to provide the gate coupling that is nearly close to that of benzene and graphene, but significantly greater than fullerene-based systems.
    Keywords: Ab initio; Coulomb blockade; graphyne; single electron transistor, ATK, Application
    Area: graphene
    BibTeX:
    @article{Sarma2014,
      author = {Sarma, J. V. N. and Chowdhury, Rajib and Jayaganthan, R.},
      title = {Graphyne-based single electron transistor: ab initio analysis},
      journal = {Nano},
      year = {2014},
      volume = {09},
      number = {03},
      pages = {1450032},
      doi = {http://dx.doi.org/10.1142/S1793292014500325}
    }
    
    Anurag Srivastava & Florina Regius Structural and Electronic Properties of Doped Silicon Nanowire 2014 International Journal of Science and Research
    Vol. 3(8), 710-716 
    URL 
    Abstract: Electronic and structural properties of Silicon Nanowire (SiNW) when doped with Al and P atoms are obtained from simulation studies have been reviewed. The bandgap , density of states and Structural property of Sillicon Nanowire has been compared when this nanowire is doped with phosphrous and aluminium atoms. We observed that decrease in bandgap increases the metallic property of silicon. Total energy is maximum then the structure is least stable. So we can say that total energy is inversely proportional to stability. In density of states, we clearly see the decline in DOS/Ev with the increase of doping Al and P atoms. In this paper, we have discussed all the electronic and structural properties.
    Keywords: Band structure, Band gap , Density of States , SINW , Aluminium, ATK, Application
    Area: nanowires
    BibTeX:
    @article{Srivastava2014c,
      author = {Anurag Srivastava and Florina Regius},
      title = {Structural and Electronic Properties of Doped Silicon Nanowire},
      journal = {International Journal of Science and Research},
      year = {2014},
      volume = {3},
      number = {8},
      pages = {710-716},
      url = {http://www.ijsr.net/archive/v3i8/MDIwMTU0Mjg=.pdf}
    }
    
    W.-F. Sun, X. Wang & Z. Sun Ab initio study of electronic structure, quantum transport and optical absorption properties of polyacene quinone radical polymers 2014 IEEE Transactions on Dielectrics and Electrical Insulation
    Vol. 21(4), 1801-1808 
    DOI  
    Abstract: Semiempirical quantum mechanical calculations have been implemented to study the molecular structure, electronic structure, optical properties of polyacene quinone radical polymers, and the quantum transport properties are also been calculated through combination of the numerical atomic orbitals basis set method based on density functional theory with the non-equilibrium Green's function formalism. The polyacene quinone radical polymers exhibit similar elastic modulus to the carbon nanotubes. The electronic molecular orbitals and energy bands of polyacene quinone radical polymers show insulator features, with the great conjugated bonds formed in polymer molecules resulting in extreme high polarization and dielectric constants, and the Fermi energy and band-gaps of ultraviolet range are static with the variation of polymerization degree. The aluminum electrodes with crystallographic (001) surfaces have been used in the electronic transport calculations, which indicate the quantum conductance spectrum changes with the varied strain and polymerization degree, however appears no explicit change, representing large open-gap feature of insulators. Ultraviolet-visible absorption spectra show a few characteristic peaks, the positions and number of which varying with polymerization degree, predicting that polyacene quinone radical polymers, as high dielectric functional materials, could be applied to ultraviolet optoelectronic nanoscale quantum devices.
    Keywords: Atom optics; Electrodes; Optical polarization; Optical polymers; Plastics; Quantum mechanics; Ab initio; electronic structure; polyacene quinone radical polymer; quantum transport; ATK; Application
    Area: molecular electronics
    BibTeX:
    @article{Sun2014,
      author = {Sun, W.-F. and Wang, X. and Sun, Z.},
      title = {Ab initio study of electronic structure, quantum transport and optical absorption properties of polyacene quinone radical polymers},
      journal = {IEEE Transactions on Dielectrics and Electrical Insulation},
      year = {2014},
      volume = {21},
      number = {4},
      pages = {1801-1808},
      doi = {http://dx.doi.org/10.1109/TDEI.2014.004331}
    }
    
    Cai Juan Xia, De Hua Zhang, Ai Min Chen & Ying Tang Zhang Effect of carbon nanotubes chirality on the E-C photo-isomerization switching behavior in moelcular device 2014 Optik
    Vol. 125(16), 4522 - 4525 
    DOI  
    Abstract: Applying nonequilibrium Green's function formalism in combination with the first-principles density functional theory, we investigate the electronic transport properties of optical molecular switch based on the fulgide molecule with two different single-walled carbon nanotube (SWCNT) electrodes. The molecule that comprises the switch can convert between E isomer and C isomer by ultraviolet or visible irradiation. Theoretical results show that these two isomers exhibit very different conductance properties both in armchair and zigzag junction, which can realize the on and off states of the molecular switch. Meantime, the chirality of the SWCNT electrodes strongly affects the switching characteristics of the molecular junctions, which is useful for the design of functional molecular devices.
    Keywords: Photo-isomerization, Molecular switch, Electronic transport, Single-walled nanotube, ATK, Application
    Area: nanotubes
    BibTeX:
    @article{Xia2014a,
      author = {Cai Juan Xia and De Hua Zhang and Ai Min Chen and Ying Tang Zhang},
      title = {Effect of carbon nanotubes chirality on the E-C photo-isomerization switching behavior in moelcular device},
      journal = {Optik},
      year = {2014},
      volume = {125},
      number = {16},
      pages = {4522 - 4525},
      doi = {http://dx.doi.org/10.1016/j.ijleo.2014.02.015}
    }
    
    Serhan Yamacli Comparison of the electronic transport properties of metallic graphene and silicene nanoribbons 2014 Journal of Nanoparticle Research
    Vol. 16(8), 2576 
    DOI  
    Abstract: Carbon-based materials such as carbon nanotubes and graphene nanoribbons are investigated extensively for the near future nanoelectronics technology. Considering the expertise on the processing of silicon, various implementations of silicon counterparts of these nanoscale components such as silicon nanotubes and silicene nanoribbons have also been reported recently. In this work, electronic transport properties of metallic graphene and silicene nanoribbons (GNRs and SiNRs) are compared. Ab initio simulations based on density functional theory combined with non-equilibrium Green's function formalism are used to obtain the voltage-dependent transmission spectra, resistance-voltage variations and the potential profiles of realistic metallic GNR and SiNR samples. The investigation of the variations of the transmission characteristics of the GNRs and SiNRs exposes that both nano structures show voltage-dependent resistances due to elastic potential scattering compliant with Büttiker formalism. However, the variation of the transmission spectra of GNRs by the applied voltage is lower than that of SiNRs indicating that metallic GNRs seem to be better candidates compared to their silicon counterparts for use as metallic interconnects.
    Keywords: Graphene; Silicene; Nanoribbons; Transmission spectrum; Voltage-dependency; Two-dimensional materials, ATK, Application
    Area: graphene
    BibTeX:
    @article{Yamacli2014b,
      author = {Yamacli, Serhan},
      title = {Comparison of the electronic transport properties of metallic graphene and silicene nanoribbons},
      journal = {Journal of Nanoparticle Research},
      publisher = {Springer Netherlands},
      year = {2014},
      volume = {16},
      number = {8},
      pages = {2576},
      doi = {http://dx.doi.org/10.1007/s11051-014-2576-y}
    }
    
    Serhan Yamacli Investigation of the voltage-dependent transport properties of metallic silicon nanotubes (SiNTs): A first-principles study 2014 Computational Materials Science
    Vol. 91, 6 - 10 
    DOI  
    Abstract: Considering that the current microelectronics technology is built upon silicon, various nanoscale silicon structures are being investigated. In this study, voltage-dependent transmission characteristics of short silicon nanotubes (SiNTs) are investigated using first-principles methods. Density functional theory in conjunction with non-equilibrium Green's function formalism is utilized to simulate metallic (5, 5) and (8, 8) SiNTs in order to obtain their current-voltage characteristics. The variation of the SiNT resistance with the applied voltage is also given and discussed together with the change in the transmission spectra. It is shown that current-voltage characteristics of short metallic SiNTs show nonlinear behaviour due to the changes in their transmission spectra. Obtained results and characteristics have implications on nanoscale SiNT interconnect design.
    Keywords: Silicon nanotubes (SiNTs), Current-voltage characteristics, Transmission spectrum, ATK, Application
    Area: nanotubes
    BibTeX:
    @article{Yamacli2014c,
      author = {Serhan Yamacli},
      title = {Investigation of the voltage-dependent transport properties of metallic silicon nanotubes (SiNTs): A first-principles study},
      journal = {Computational Materials Science },
      year = {2014},
      volume = {91},
      pages = {6 - 10},
      doi = {http://dx.doi.org/10.1016/j.commatsci.2014.04.044}
    }
    
    Shenlang Yan, Mengqiu Long, Xiaojiao Zhang, Jun He, Hui Xu & Keqiu Chen Effects of the magnetic anchoring groups on spin-dependent transport properties of Ni(dmit)2 device 2014 Chemical Physics Letters
    Vol. 608, 28 - 34 
    DOI  
    Abstract: By using non-equilibrium Green's functions in combination with the density functional theory, we investigated the spin-dependent electronic transport properties through a single-molecule-magnet (SMM) Ni(dmit)2 between two nanoscale Au(1 1 1) electrodes with different anchoring groups. The nonmagnetic (S) and magnetic (Ni, Mn) anchoring groups have been chosen. Our results show that the spin-dependent electronic transport properties can be modulated significantly by the anchoring groups, and many interesting phenomena such as high spin-filtering ratio, rectifying and negative differential resistance can be observed. These characteristics could be used in the study of spin physics and the realization of nano-spintronic devices based on SMMs.
    Keywords: ATK, Application, spin-dependent transport
    Area: molecular electronics, spintronics
    BibTeX:
    @article{Yan2014a,
      author = {Shenlang Yan and Mengqiu Long and Xiaojiao Zhang and Jun He and Hui Xu and Keqiu Chen},
      title = {Effects of the magnetic anchoring groups on spin-dependent transport properties of Ni(dmit)2 device},
      journal = {Chemical Physics Letters},
      year = {2014},
      volume = {608},
      pages = {28 - 34},
      doi = {http://dx.doi.org/10.1016/j.cplett.2014.05.060}
    }
    
    Haiping Yu, Jiming Zheng, Ping Guo & Zhiyong Zhang Spin transport properties of a carbon nanotube/zigzag graphene nanoribbon junction: a first principles investigation 2014 Applied Physics A
    Vol. 117(4), 2175-2181 
    DOI  
    Abstract: A carbon nanotube (CNT)/zigzag graphene nanoribbons (ZGNRs) junctions has been proposed and investigated by first-principles calculations. The results show that large spin polarization of currents would be achieved when only one edge of ZGNR is coupled to the other lead. By virtue of spatial separation of edge state in two spin channel, one of those channels is opened at certain energy range and gives rise to spin-polarized currents under a low bias. This feature is stable whenever the ZGNR lead is under the antiferromagnetic ground states or is under the ferromagnetic states. Our findings indicate that this approach is simple and efficient for spintronics design.
    Keywords: ATK, Application, spin transport, carbon nanotube, graphene nanoribbon
    Area: graphene, nanotube, spintronics
    BibTeX:
    @article{Yu2014,
      author = {Yu, Haiping and Zheng, Jiming and Guo, Ping and Zhang, Zhiyong},
      title = {Spin transport properties of a carbon nanotube/zigzag graphene nanoribbon junction: a first principles investigation},
      journal = {Applied Physics A},
      publisher = {Springer Berlin Heidelberg},
      year = {2014},
      volume = {117},
      number = {4},
      pages = {2175-2181},
      doi = {http://dx.doi.org/10.1007/s00339-014-8641-7}
    }
    
    Jingfen Zhao, Wenkai Zhao, Bin Cui, Changfeng Fang, Yuqing Xu, Xiangru Kong, Dongmei Li & Desheng Liu Electronic transport properties of a dithienylethene-based polymer with different metallic contacts 2014 RSC Advances
    Vol. 4, 40941-40950 
    DOI  
    Abstract: We have studied the electronic transport behaviors of a dithienylethene-based polymer between two metal surfaces using nonequilibrium Green's functions combined with density functional theory. The present computational results show that the polymer with closed and open configurations really demonstrates switching behavior which confirms the experimental observation. It is also found that the switching behavior depends on the electronic properties of two configurations of polymer instead of the contact modes. The on-off ratios of conductance between the closed and open configurations reach up to two orders of magnitude. Negative differential resistance and rectification phenomena are also observed in such systems.
    Keywords: ATK, Application, polymers, electronic transport
    Area: molecular electronics
    BibTeX:
    @article{Zhao2014b,
      author = {Zhao, Jingfen and Zhao, Wenkai and Cui, Bin and Fang, Changfeng and Xu, Yuqing and Kong, Xiangru and Li, Dongmei and Liu, Desheng},
      title = {Electronic transport properties of a dithienylethene-based polymer with different metallic contacts},
      journal = {RSC Advances},
      publisher = {The Royal Society of Chemistry},
      year = {2014},
      volume = {4},
      pages = {40941-40950},
      doi = {http://dx.doi.org/10.1039/C4RA06904H}
    }
    
    P. Zhao, Q.H. Wu, H.Y. Liu, D.S. Liu & G. Chen A first-principles study of the spin transport properties of a 4H-TAHDI-based multifunctional spintronic device with graphene nanoribbon electrodes 2014 J. Mater. Chem. C
    Vol. 2(32), 6648 
    DOI  
    Abstract: By using the nonequilibrium Green's function formalism in combination with the density functional theory, we have investigated the spin transport properties of a 4H-TAHDI-based multifunctional spintronic device constructed by contacting a 4H-TAHDI molecule with two ferromagnetic zigzag-edge graphene nanoribbon electrodes. The results show that perfect giant magnetoresistance, spin-filtering, bipolar spin-rectifying, and negative differential resistance effects can be realized simultaneously. The mechanisms were proposed for these interesting phenomena. Our results demonstrate that this system holds promise in the design of a high-performance multifunctional single-molecule spintronic device.
    Keywords: ATK, Application, spin transport, graphene, nanoribbon
    Area: graphene, spintronics
    BibTeX:
    @article{Zhao2014c,
      author = {Zhao, P. and Wu, Q. H. and Liu, H. Y. and Liu, D. S. and Chen, G.},
      title = {A first-principles study of the spin transport properties of a 4H-TAHDI-based multifunctional spintronic device with graphene nanoribbon electrodes},
      journal = {J. Mater. Chem. C},
      publisher = {Royal Society of Chemistry (RSC)},
      year = {2014},
      volume = {2},
      number = {32},
      pages = {6648},
      doi = {http://dx.doi.org/10.1039/c4tc00895b}
    }
    
    Towfiq Ahmed, Jason T. Haraldsen, Jian-Xin Zhu & Alexander V. Balatsky Next-Generation Epigenetic Detection Technique: Identifying Methylated Cytosine Using Graphene Nanopore 2014 The Journal of Physical Chemistry Letters
    Vol. 5(15), 2601-2607 
    DOI  
    Abstract: DNA methylation plays a pivotal role in the genetic evolution of both embryonic and adult cells. For adult somatic cells, the location and dynamics of methylation have been very precisely pinned down with the 5-cytosine markers on cytosine-phosphate-guanine (CpG) units. Unusual methylation on CpG islands is identified as one of the prime causes for silencing the tumor suppressant genes. Early detection of methylation changes can diagnose the potentially harmful oncogenic evolution of cells and provide promising guideline for cancer prevention. With this motivation, we propose a cytosine methylation detection technique. Our hypothesis is that electronic signatures of DNA acquired as a molecule translocates through a nanopore would be significantly different for methylated and nonmethylated bases. This difference in electronic fingerprints would allow for reliable real-time differentiation of methylated DNA. We calculate transport currents through a punctured graphene membrane while the cytosine and methylated cytosine translocate through the nanopore. We also calculate the transport properties for uracil and cyanocytosine for comparison. Our calculations of transmission, current, and tunneling conductance show distinct signatures in their spectrum for each molecular type. Thus, in this work, we provide a theoretical analysis that points to a viability of our hypothesis.
    Keywords: ATK, application, graphene, cytosine
    Area: graphene
    BibTeX:
    @article{Ahmed2014a,
      author = {Ahmed, Towfiq and Haraldsen, Jason T. and Zhu, Jian-Xin and Balatsky, Alexander V.},
      title = {Next-Generation Epigenetic Detection Technique: Identifying Methylated Cytosine Using Graphene Nanopore},
      journal = {The Journal of Physical Chemistry Letters},
      year = {2014},
      volume = {5},
      number = {15},
      pages = {2601-2607},
      doi = {http://dx.doi.org/10.1021/jz501085e}
    }
    
    Feras Al-Dirini, Faruque M. Hossain, Ampalavanapillai Nirmalathas & Efstratios Skafidas All-Graphene Planar Double Barrier Resonant Tunneling Diodes 2014 Journal of the Electron Devices Society
    Vol. 2(5), 118-122 
    DOI  
    Abstract: In this work, we propose an atomically-thin all-graphene planar double barrier resonant tunneling diode that can be realized within a single graphene nanoribbon. The proposed device does not require any doping or external gating and can be fabricated using minimal process steps. The planar architecture of the device allows a simple in-plane connection of multiple devices in parallel without any extra processing steps during fabrication, enhancing the current driving capabilities of the device. Quantum mechanical simulation results, based on non-equilibrium Green's function formalism and the extended Huckel method, show promising device performance with a high reverse-to-forward current rectification ratio exceeding 50 000, and confirm the presence of negative differential resistance within the device's current-voltage characteristics.
    Keywords: Double barrierer, extended Huckel, graphene, planar diode, resonant tunneling, rectifier, NDR, NEGF, ATK, Application
    Area: graphene
    BibTeX:
    @article{Al-Dirini2014a,
      author = {Al-Dirini, Feras and Hossain, Faruque M. and Nirmalathas, Ampalavanapillai and Skafidas, Efstratios},
      title = {All-Graphene Planar Double Barrier Resonant Tunneling Diodes},
      journal = {Journal of the Electron Devices Society},
      publisher = {Institute of Electrical & Electronics Engineers (IEEE)},
      year = {2014},
      volume = {2},
      number = {5},
      pages = {118-122},
      doi = {http://dx.doi.org/10.1109/jeds.2014.2327375}
    }
    
    G.R. Berdiyorov, M.V. Milosevic, F.M. Peeters & Adri C.T. van Duin Stability of CH3 molecules trapped on hydrogenated sites of graphene 2014 Physica B: Condensed Matter
    Vol. 455, 60 - 65 
    DOI  
    Abstract: We study the effect of a hydrogen atom on the thermal stability of a trapped CH3 molecule on graphene using ReaxFF molecular dynamics simulations. Due to the hydrogen-molecule interaction, enhanced pinning of the CH3 molecule is observed when it is positioned adjacent to the graphene site with the hydrogen atom. We discuss the formation process of such a stable configuration, which originates from different adhesion and migration energies of the hydrogen atom and the CH3 molecule. We also studied the effect of the CH3-H configuration on the electronic transport properties of graphene nanoribbons using first principles density-functional calculations. We found that the formation of the CH3-H structure results in extra features in the transmission spectrum due to the formation of strongly localized states, which are absent when the CH3 molecule is trapped on pristine graphene. Our findings will be useful in exploiting gas sensing properties of graphene, especially for selective detection of individual molecules.
    Keywords: Graphene, Molecular dynamics, Electronic transport, ATK, Application
    Area: graphene
    BibTeX:
    @article{Berdiyorov2014,
      author = {G.R. Berdiyorov and M.V. Milosevic and F.M. Peeters and Adri C.T. van Duin},
      title = {Stability of CH3 molecules trapped on hydrogenated sites of graphene},
      journal = {Physica B: Condensed Matter},
      year = {2014},
      volume = {455},
      pages = {60 - 65},
      note = {21st Latin American Symposium on Solid State Physics - SLAFES 2013},
      doi = {http://dx.doi.org/10.1016/j.physb.2014.07.046}
    }
    
    Anuja Chanana & Santanu Mahapatra Theoretical Insights to Niobium-Doped Monolayer MoS2-Gold Contact 2015 IEEE Transactions on Electron Devices
    Vol. 62(7), 2346-2351 
    DOI  
    Abstract: We report a first principles study of the electronic properties for a contact formed between Nb-doped monolayer MoS2 and gold for different doping concentrations. We first focus on the shift of energy levels in band structure and the density of states with respect to the Fermi level for a geometrically optimized 5 × 5 MoS2 supercell for both pristine and Nb-doped structures. The doping is achieved by substituting Mo atoms with Nb atoms at random positions. It is observed that for an experimentally reported sheet hole doping concentration of 1.8 × 1014 cm2, the pristine MoS2 converts to degenerate p-type semiconductor. Next, we interface this supercell with six layers of (111) cleaved surface of gold to investigate the contact nature of MoS2-Au system. By careful examination of projected band structure, projected density of states, effective potential and charge density difference, we demonstrate that the Schottky barrier nature observed for pure MoS2-Au contact can be converted from n-type to p-type by efficient Nb doping.
    Keywords: doping, MoS2, niobium, Schottky barrier, ATK, Application, TMD
    Area: interfaces, graphene
    BibTeX:
    @article{Chanana2015,
      author = {Chanana, Anuja and Mahapatra, Santanu},
      title = {Theoretical Insights to Niobium-Doped Monolayer MoS2-Gold Contact},
      journal = {IEEE Transactions on Electron Devices},
      publisher = {Institute of Electrical & Electronics Engineers (IEEE)},
      year = {2015},
      volume = {62},
      number = {7},
      pages = {2346-2351},
      doi = {http://dx.doi.org/10.1109/ted.2015.2433931}
    }
    
    C.J. Dai, X.H. Yan, Y. Xiao & Y.D. Guo Electronic and transport properties of T-graphene nanoribbon: Symmetry-dependent multiple Dirac points, negative differential resistance and linear current-bias characteristics 2014 Europhysics Letters
    Vol. 107(3), 37004 
    DOI  
    Abstract: Based on the tight-binding method and density functional theory, band structures and transport properties of T-graphene nanoribbons are investigated. By constructing and solving the tight-binding Hamiltonian, we derived the analytic expressions of the linear dispersion relation and Fermi velocity of Dirac-like fermions for armchair T-graphene nanoribbons. Multiple Dirac points, which are triggered by the mirror symmetry of armchair T-graphene nanoribbons, are observed. The number and positions of multiple Dirac points can be well explained by our analytic expressions. Tight-binding results are confirmed by the results from density functional calculations. Moreover, armchair T-graphene nanoribbons exhibit negative differential resistance, whereas zigzag T-graphene nanoribbons have linear current-bias voltage characteristics near the Fermi level.
    Keywords: ATK, Application, electronic, transport, nanoribbon, Dirac point, negative differential resistance, ATK, application
    Area: graphene
    BibTeX:
    @article{Dai2014a,
      author = {C. J. Dai and X. H. Yan and Y. Xiao and Y. D. Guo},
      title = {Electronic and transport properties of T-graphene nanoribbon: Symmetry-dependent multiple Dirac points, negative differential resistance and linear current-bias characteristics},
      journal = {Europhysics Letters},
      year = {2014},
      volume = {107},
      number = {3},
      pages = {37004},
      doi = {http://dx.doi.org/10.1209/0295-5075/107/37004}
    }
    
    Yuanyuan He, Jinjiang Zhang & Jianwei Zhao Electron Transport and CO Sensing Characteristics of Fe(II) Porphyrin with Single-Walled Carbon Nanotube Electrodes 2014 The Journal of Physical Chemistry C
    Vol. 118(32), 18325-18333 
    DOI  
    Abstract: Electron transport and carbon monoxide (CO) sensitive characteristics of Fe(II) porphyrin (PP-Fe) with two single-walled carbon nanotube electrodes (SWCNTs) were studied using nonequilibrium Green's function (NEGF) formalism combined first-principles density functional theory (DFT). When PP-Fe is connected to SWCNT electrodes in diagonal configuration, owing to the fact that the electron passes through the Fe center, it shows higher CO sensitivity than that in para connection mode. Meanwhile, the PP-Fe sensor with armchair SWCNTs is more sensitive to CO than that in zigzag junction, since the coupling interaction between central molecule and armchair SWCNT electrodes is stronger. The PP-Fe sensor anchored on armchair SWCNTs in diagonal configuration can reach a current on-off ratio of 2.1 x 104 in response to the chemisorption of CO, showing better CO sensitive characteristics than that with zigzag SWCNTs and metallic electrodes. With the development of experimental techniques, it is completely possible to fabricate this kind of CO sensor by experimental means.
    Keywords: ATK, Application, electron transport, sensing, carbon nanotube
    Area: nanotubes
    BibTeX:
    @article{He2014b,
      author = {He, Yuanyuan and Zhang, Jinjiang and Zhao, Jianwei},
      title = {Electron Transport and CO Sensing Characteristics of Fe(II) Porphyrin with Single-Walled Carbon Nanotube Electrodes},
      journal = {The Journal of Physical Chemistry C},
      year = {2014},
      volume = {118},
      number = {32},
      pages = {18325-18333},
      doi = {http://dx.doi.org/10.1021/jp502534d}
    }
    
    Faruque M. Hossain, Feras Al-Dirini & Efstratios Skafidas Contactless electronic transport in a bio-molecular junction 2014 Applied Physics Letters
    Vol. 105(4), - 
    DOI URL 
    Abstract: Molecular electronics hold promise for next generation ultra-low power, nano-scale integrated electronics. The main challenge in molecular electronics is to make a reliable interface between molecules and metal electrodes. Interfacing metals and molecules detrimentally affects the characteristics of nano-scale molecular electronic devices. It is therefore essential to investigate alternative arrangements such as contact-less tunneling gaps wherever such configurations are feasible. We conduct ab initio density functional theory and non-equilibrium Green's functions calculations to investigate the transport properties of a biocompatible glycine molecular junction. By analyzing the localized molecular orbital energy distributions and transmission probabilities in the transport-gap, we find a glycine molecule confined between two gold electrodes, without making a contact, is energetically stable and possesses high tunneling current resembling an excellent ohmic-like interface.
    Keywords: ATK, Application, electron transport, molecular junction
    Area: molecular electronics
    BibTeX:
    @article{Hossain2014a,
      author = {Hossain, Faruque M. and Al-Dirini, Feras and Skafidas, Efstratios},
      title = {Contactless electronic transport in a bio-molecular junction},
      journal = {Applied Physics Letters},
      year = {2014},
      volume = {105},
      number = {4},
      pages = {-},
      url = {http://scitation.aip.org/content/aip/journal/apl/105/4/10.1063/1.4891857},
      doi = {http://dx.doi.org/10.1063/1.4891857}
    }
    
    Jiahao Kang, Wei Liu, Deblina Sarkar, Debdeep Jena & Kaustav Banerjee Computational Study of Metal Contacts to Monolayer Transition-Metal Dichalcogenide Semiconductors 2014 Physical Review X
    Vol. 4, 031005 
    DOI  
    Abstract: Among various 2D materials, monolayer transition-metal dichalcogenide (mTMD) semiconductors with intrinsic band gaps (1-2 eV) are considered promising candidates for channel materials in next-generation transistors. Low-resistance metal contacts to mTMDs are crucial because currently they limit mTMD device performances. Hence, a comprehensive understanding of the atomistic nature of metal contacts to these 2D crystals is a fundamental challenge, which is not adequately addressed at present. In this paper, we report a systematic study of metal-mTMD contacts with different geometries (top contacts and edge contacts) by ab initio density-functional theory calculations, integrated with Mulliken population analysis and a semiempirical van der Waals dispersion potential model (which is critical for 2D materials and not well treated before). Particularly, In, Ti, Au, and Pd, contacts to monolayer MoS2 and WSe2 as well as Mo-MoS2 and W-WSe2 contacts are evaluated and categorized, based on their tunnel barriers, Schottky barriers, and orbital overlaps. Moreover, going beyond Schottky theory, new physics in such contact interfaces is revealed, such as the metallization of mTMDs and abnormal Fermi level pinning. Among the top contacts to MoS2, Ti and Mo show great potential to form favorable top contacts, which are both n-type contacts, while for top contacts to WSe2, W or Pd exhibits the most advantages as an n- or p-type contact, respectively. Moreover, we find that edge contacts can be highly advantageous compared to top contacts in terms of electron injection efficiency. Our formalism and the results provide guidelines that would be invaluable for designing novel 2D semiconductor devices.
    Keywords: Computational Physics, Electronics, Nanophysics, ATK, Application, metal contact, TMD
    Area: interfaces, graphene
    BibTeX:
    @article{Kang2014,
      author = {Kang, Jiahao and Liu, Wei and Sarkar, Deblina and Jena, Debdeep and Banerjee, Kaustav},
      title = {Computational Study of Metal Contacts to Monolayer Transition-Metal Dichalcogenide Semiconductors},
      journal = {Physical Review X},
      publisher = {American Physical Society},
      year = {2014},
      volume = {4},
      pages = {031005},
      doi = {http://dx.doi.org/10.1103/PhysRevX.4.031005}
    }
    
    Xin-Mei Li, Meng-Qiu Long, Li-Ling Cui, Jin Xiao, Xiao-Jiao Zhang, Dan Zhang & Hui Xu Effects of V-shaped edge defect and H-saturation on spin-dependent electronic transport of zigzag MoS2 nanoribbons 2014 Physics Letters A
    Vol. 378(36), 2701 - 2707 
    DOI  
    Abstract: Based on nonequilibrium Green's function in combination with density functional theory calculations, the spin-dependent electronic transport properties of one-dimensional zigzag molybdenum disulfide (MoS2) nanoribbons with V-shaped defect and H-saturation on the edges have been studied. Our results show that the spin-polarized transport properties can be found in all the considered zigzag MoS2 nanoribbons systems. The edge defects, especially the V-shaped defect on the Mo edge, and H-saturation on the edges can suppress the electronic transport of the systems. Also, the spin-filtering and negative differential resistance behaviors can be observed obviously. The mechanisms are proposed for these phenomena.
    Keywords: Zigzag MoS2 nanoribbons, V-shaped edge defect, H-saturation, Spin-dependent transport property, Negative differential resistance, ATK, Application
    Area: graphene, spin
    BibTeX:
    @article{Li2014e,
      author = {Xin-Mei Li and Meng-Qiu Long and Li-Ling Cui and Jin Xiao and Xiao-Jiao Zhang and Dan Zhang and Hui Xu},
      title = {Effects of V-shaped edge defect and H-saturation on spin-dependent electronic transport of zigzag MoS2 nanoribbons},
      journal = {Physics Letters A },
      year = {2014},
      volume = {378},
      number = {36},
      pages = {2701 - 2707},
      doi = {http://dx.doi.org/10.1016/j.physleta.2014.07.024}
    }
    
    Zeyuan Ni, Hongxia Zhong, Xinhe Jiang, Ruge Quhe, Guangfu Luo, Yangyang Wang, Meng Ye, Jinbo Yang, Junjie Shi & Jing Lu Tunable band gap and doping type in silicene by surface adsorption: towards tunneling transistors 2014 Nanoscale
    Vol. 6(13), 7609-7618 
    DOI  
    Abstract: By using first-principles calculations, we predict that a sizable band gap can be opened at the Dirac point of silicene without degrading silicene's electronic properties with n-type doping by Cu, Ag, and Au adsorption, p-type doping by Ir adsorption, and neutral doping by Pt adsorption. A silicene p-i-n tunneling field effect transistor (TFET) model is designed by the adsorption of different transition metal atoms on different regions of silicene. Quantum transport simulations demonstrate that silicene TFETs have an on-off ratio of 103, a small sub-threshold swing of 77 mV dec-1, and a large on-state current of over 1 mA mm-1 under a supply voltage of about 1.7 V.
    Keywords: ATK, Application, band gap, silicene, adsorption, tunneling transistor
    Area: graphene
    BibTeX:
    @article{Ni2014a,
      author = {Ni, Zeyuan and Zhong, Hongxia and Jiang, Xinhe and Quhe, Ruge and Luo, Guangfu and Wang, Yangyang and Ye, Meng and Yang, Jinbo and Shi, Junjie and Lu, Jing},
      title = {Tunable band gap and doping type in silicene by surface adsorption: towards tunneling transistors},
      journal = {Nanoscale},
      publisher = {Royal Society of Chemistry (RSC)},
      year = {2014},
      volume = {6},
      number = {13},
      pages = {7609-7618},
      doi = {http://dx.doi.org/10.1039/c4nr00028e}
    }
    
    Wanzhi Qiu & Efstratios Skafidas Graphene nanopore field effect transistors 2014 Journal of Applied Physics
    Vol. 116(2), 023709 
    DOI  
    Abstract: Graphene holds great promise for replacing conventional Si material in field effect transistors (FETs) due to its high carrier mobility. Previously proposed graphene FETs either suffer from low ON-state current resulting from constrained channel width or require complex fabrication processes for edge-defecting or doping. Here, we propose an alternative graphene FET structure created on intrinsic metallic armchair-edged graphene nanoribbons with uniform width, where the channel region is made semiconducting by drilling a pore in the interior, and the two ends of the nanoribbon act naturally as connecting electrodes. The proposed GNP-FETs have high ON-state currents due to seamless atomic interface between the channel and electrodes and are able to be created with arbitrarily wide ribbons. In addition, the performance of GNP-FETs can be tuned by varying pore size and ribbon width. As a result, their performance and fabrication process are more predictable and controllable in comparison to schemes based on edge-defects and doping. Using first-principle transport calculations, we show that GNP-FETs can achieve competitive leakage current of ~70 pA, subthreshold swing of ~60 mV/decade, and significantly improved On/Off current ratios on the order of 105 as compared with other forms of graphene FETs.
    Keywords: ATK, application, graphene, FET, field effect transistor
    Area: graphene, spin
    BibTeX:
    @article{Qiu2014c,
      author = {Qiu, Wanzhi and Skafidas, Efstratios},
      title = {Graphene nanopore field effect transistors},
      journal = {Journal of Applied Physics},
      year = {2014},
      volume = {116},
      number = {2},
      pages = {023709},
      doi = {http://dx.doi.org/10.1063/1.4889755}
    }
    
    Sabyasachi Sen & Swapan Chakrabarti Graphitic Silicon Nitride: A Metal-Free Ferromagnet with Charge and Spin Current Rectification 2014 ChemPhysChem
    Vol. 15(13), 2756-2761 
    DOI  
    Abstract: As a first example, herein we show that g-Si4N3 is expected to act as a metal-free ferromagnet featuring both charge and spin current rectification simultaneously. Such rectification is crucial for envisioning devices that contain both logic and memory functionality on a single chip. The spin coherent quantum-transport calculations on g-Si4N3 reveal that the chosen system is a unique molecular spin filter, the current-voltage characteristics of which is asymmetric in nature, which can create a perfect background for synchronous charge and spin current rectification. To shed light on this highly unusual in-silico observation, we have meticulously inspected the bias-dependent modulation of the spin-polarized eigenstates. The results indicate that, whereas only the localized 2p orbitals of the outer-ring (OR) Si atoms participate in the transmission process in the positive bias, both OR Si and N atoms contribute in the reverse bias. Furthermore, we have evaluated the spin-polarized electron-transfer rate in the tunneling regime, and the results demonstrate that the transfer rates are unequal in the positive and negative bias range, leading to the possible realization of a simultaneous logic-memory device.
    Keywords: charge transfer, density functional calculations, magnetic properties, quantum chemistry, semiconductors, ATK, Application
    Area: semi, spin
    BibTeX:
    @article{Sen2014a,
      author = {Sen, Sabyasachi and Chakrabarti, Swapan},
      title = {Graphitic Silicon Nitride: A Metal-Free Ferromagnet with Charge and Spin Current Rectification},
      journal = {ChemPhysChem},
      publisher = {WILEY-VCH Verlag},
      year = {2014},
      volume = {15},
      number = {13},
      pages = {2756--2761},
      doi = {http://dx.doi.org/10.1002/cphc.201402265}
    }
    
    Pankaj Srivastava, Subhra Dhar & Neeraj K. Jaiswal Ab initio study of gold-doped zigzag graphene nanoribbons 2014 Applied Physics A
    Vol. 117(4), 1997-2008 
    DOI  
    Abstract: The electronic transport properties of zigzag graphene nanoribbons (ZGNRs) through covalent functionalization of gold (Au) atoms is investigated by using non-equilibrium Green's function combined with density functional theory. It is revealed that the electronic properties of Au-doped ZGNRs vary significantly due to spin and its non-inclusion. We find that the DOS profiles of Au-adsorbed ZGNR due to spin reveal very less number of states available for conduction, whereas non-inclusion of spin results in higher DOS across the Fermi level. Edge Au-doped ribbons exhibit stable structure and are energetically more favorable than the center Au-doped ZGNRs. Though the chemical interaction at the ZGNR-Au interface modifies the Fermi level, Au-adsorbed ZGNR reveals semimetallic properties. A prominent qualitative change of the I-V curve from linear to nonlinear is observed as the Au atom shifts from center toward the edges of the ribbon. Number of peaks present near the Fermi level ensures conductance channels available for charge transport in case of Au-center-substituted ZGNR. We predict semimetallic nature of the Au-adsorbed ZGNR with a high DOS peak distributed over a narrow energy region at the Fermi level and fewer conductance channels. Our calculations for the magnetic properties predict that Au functionalization leads to semiconducting nature with different band gaps for spin up and spin down. The outcomes are compared with the experimental and theoretical results available for other materials.
    Keywords: ATK, Application, gold, graphene, nanoribbon, electron transport
    Area: graphene
    BibTeX:
    @article{Srivastava2014d,
      author = {Srivastava, Pankaj and Dhar, Subhra and Jaiswal, Neeraj K.},
      title = {Ab initio study of gold-doped zigzag graphene nanoribbons},
      journal = {Applied Physics A},
      publisher = {Springer Berlin Heidelberg},
      year = {2014},
      volume = {117},
      number = {4},
      pages = {1997-2008},
      doi = {http://dx.doi.org/10.1007/s00339-014-8608-8}
    }
    
    Kurt Stokbro & Søren Smidstrup Atomic-scale modelling of electron transport across metal-organic interfaces 2014 International Workshop on Computational Electronics  URL 
    Abstract: We study the atomic and electronic structure of a metal-organic interface using Density Functional Theory combined with Non-Equilibrium Greens Functions (DFT-NEGF). We calculate the I-V characteristics of the interface and find strong rectification. The electro-static potential shows the formation of a Schottky barrier contact, and we present a new model for transport across an organic semiconductor Schottky barrier which can rationalize the simulation data.
    Keywords: ATK, Application, electron transport, metal-organic interface, Schottky barrier, rectification
    Area: interfaces
    BibTeX:
    @inproceedings{Stokbro2014,
      author = {Kurt Stokbro and Søren Smidstrup},
      title = {Atomic-scale modelling of electron transport across metal-organic interfaces},
      booktitle = {International Workshop on Computational Electronics},
      year = {2014},
      url = {http://in4.iue.tuwien.ac.at/pdfs/iwce/iwce17_2014/IWCE_2014_133-134.pdf}
    }
    
    Dan-Dan Wu, Hua-Hua Fu, Lei Gu, Yun Ni, Feng-Xia Zu & Kai-Lun Yao Thermal spin filtering, thermal spin switching and negative-differential-resistance in thermal spin currents in zigzag SiC nanoribbons 2014 Phys. Chem. Chem. Phys.
    Vol. 16, 17493-17498 
    DOI  
    Abstract: Spin caloritronics with a combination of spintronics and thermoelectrics has potential applications in future information science and opens a new direction in the development of multi-functional materials. Based on density functional theory and the nonequilibrium Green's function method, we calculate thermal spin-dependent transport through a zigzag silicon carbide nanoribbon (ZSiCNR), which is a heterojunction consisting of a left electrode (ZSiC-2H1H) and right electrode terminated (ZSiC-1H1H) by hydrogen. Our results show that when the temperature in the left contact increases over a critical value, the thermal spin-down current increases remarkably from zero, while the thermal spin-up current remains zero in the total-temperature region, indicating that a perfect thermal spin filter together with a perfect spin switcher is obtained. Furthermore, the thermal spin current shows a negative differential resistance effect and quantum oscillation behaviors. These results suggest that the zigzag SiC nanoribbon proposed by us can be designed as a highly-efficient spin caloritronics device with multiple functionalities.
    Keywords: ATK, Application, spin filtering, spin switching, negative differential resistance, spin current, SiC, silicon carbide, nanoribbon
    Area: graphene, spin
    BibTeX:
    @article{Wu2014,
      author = {Wu, Dan-Dan and Fu, Hua-Hua and Gu, Lei and Ni, Yun and Zu, Feng-Xia and Yao, Kai-Lun},
      title = {Thermal spin filtering, thermal spin switching and negative-differential-resistance in thermal spin currents in zigzag SiC nanoribbons},
      journal = {Phys. Chem. Chem. Phys.},
      publisher = {The Royal Society of Chemistry},
      year = {2014},
      volume = {16},
      pages = {17493-17498},
      doi = {http://dx.doi.org/10.1039/C4CP01886A}
    }
    
    Ming-Xing Zhai, Xue-Feng Wang, P. Vasilopoulos, Yu-Shen Liu, Yao-Jun Dong, Liping Zhou, Yong-Jing Jiang & Wen-Long You Giant magnetoresistance and spin Seebeck coefficient in zigzag alpha-graphyne nanoribbons 2014 Nanoscale
    Vol. 6, 11121-11129 
    DOI  
    Abstract: We investigate the spin-dependent electric and thermoelectric properties of ferromagnetic zigzag [small alpha]-graphyne nanoribbons (Z-alpha-GNRs) using density-functional theory combined with non-equilibrium Green's function method. A giant magnetoresistance is obtained in the pristine even-width Z-alpha-GNRs and can be as high as 106%. However, for the doped systems, a large magnetoresistance behavior may appear in the odd-width Z- alpha-GNRs rather than the even-width ones. This suggests that the magnetoresistance can be manipulated in a wide range by the dopants on the edges of Z-alpha-GNRs. Another interesting phenomenon is that in the B- and N-doped even-width Z-a-GNRs the spin Seebeck coefficient is always larger than the charge Seebeck coefficient, and a pure-spin-current thermospin device can be achieved at specific temperatures.
    Keywords: ATK, Application, giant magnetoresistance, Seebeck coefficient, graphyne
    Area: graphene, thermo
    BibTeX:
    @article{Zhai2014,
      author = {Zhai, Ming-Xing and Wang, Xue-Feng and Vasilopoulos, P. and Liu, Yu-Shen and Dong, Yao-Jun and Zhou, Liping and Jiang, Yong-Jing and You, Wen-Long},
      title = {Giant magnetoresistance and spin Seebeck coefficient in zigzag alpha-graphyne nanoribbons},
      journal = {Nanoscale},
      publisher = {The Royal Society of Chemistry},
      year = {2014},
      volume = {6},
      pages = {11121-11129},
      doi = {http://dx.doi.org/10.1039/C4NR02426E}
    }
    
    Adila Syaidatul Binti Azman Performance evaluation of multiple-channel armchair graphene nanoribbon field-effect transistor 2014 School: Universiti Teknologi Malaysia  URL 
    Abstract: Optimized performance with maximized packing density and ability to deliver sufficient current are highly desirable in electronic devices like transistor. By 2015, it is predicted that the transistors will be manufactured with 9 nm technology. The dimensions of the transistors are so small that the conventional metal-oxide semiconductor field-effect transistors (MOSFETs) are no longer able to retain Moore's law due to short-channel effect. Hence, new materials such as strained silicon, high-k metal, silicon nanowire, carbon nanotube (CNT), graphene and graphene nanoribbon (GNR) are introduced. A number of studies have demonstrated various ways of fabricating array-channel graphene-based field-effect transistors (FETs). This thesis describes the performance evaluation of armchair graphene nanoribbon field-effect transistor (AGNR FET) with multiple channels. Energy band structures, transmission spectra, density of states and current-voltage (I-V) characteristic curves of single and multiple-channel AGNR FETs are extracted from the simulation using Atomistix Tool Kit (ATK) software version 13.8.1 from Quantum Wise. From the study, it is proven that the energy band gap of armchair graphene nanoribbon (AGNR) increases as the nanoribbon width is decreased. Its density of states and transmission coefficient also increase linearly with the number of conducting channels. It is also proven that the multiple-channel AGNR FET exhibits higher ON current compared to single-channel AGNR FET. The outcomes of this study indicate the feasibility of using multiple conducting channels AGNR FET.
    Keywords: ATK, Application, graphene, FET
    Area: graphene
    BibTeX:
    @mastersthesis{Azman2014,
      author = {Adila Syaidatul Binti Azman},
      title = {Performance evaluation of multiple-channel armchair graphene nanoribbon field-effect transistor},
      school = {Universiti Teknologi Malaysia},
      year = {2014},
      url = {http://portal.fke.utm.my/fkelibrary/files/adilasyaidatulbintiazman/2014/788_ADILASYAIDATULBINTIAZMAN2014.pdf}
    }
    
    S. Caliskan & A. Laref The anchoring effect on the spin transport properties and I-V characteristics of pentacene molecular devices suspended between nickel electrodes 2014 Phys. Chem. Chem. Phys.
    Vol. 16, 13191-13208 
    DOI  
    Abstract: Spin-polarized transport properties are determined for pentacene sandwiched between Ni surface electrodes with various anchoring ligands. These calculations are carried out using spin density functional theory in tandem with a non-equilibrium Green's function technique. The presence of a Se atom at the edge of the pentacene molecule significantly modifies the transport properties of the device because Se has a different electronegativity than S. Our theoretical results clearly show a larger current for spin-up electrons than for spin-down electrons in the molecular junction that is attached asymmetrically across the Se linker at one side of the Ni electrodes (in an APL magnetic orientation). Moreover, this molecular junction exhibits pronounced NDR as the bias voltage is increased from 0.8 to 1.0 V. However, this novel NDR behavior is only detected in this promising pentacene molecular device. The NDR in the current-voltage (I-V) curve results from the narrowness of the density of states for the molecular states. The feasibility of controlling the TMR is also predicted in these molecular device nanostructures. Spin-dependent transmission calculations show that the sign and strength of the current-bias voltage characteristics and the TMR could be tailored for the organic molecule devices. These molecular junctions are joined symmetrically and asymmetrically between Ni metallic probes across the S and Se atoms (at the ends of the edges of the pentacene molecule). Our theoretical findings show that spin-valve phenomena can occur in these prototypical molecular junctions. The TMR and NDR results show that nanoscale junctions with spin valves could play a vital role in the production of novel functional molecular devices.
    Keywords: ATK, Application, spin transport, pentacene, nickel
    Area: molecular electronics
    BibTeX:
    @article{Caliskan2014a,
      author = {Caliskan, S. and Laref, A.},
      title = {The anchoring effect on the spin transport properties and I-V characteristics of pentacene molecular devices suspended between nickel electrodes},
      journal = {Phys. Chem. Chem. Phys.},
      publisher = {The Royal Society of Chemistry},
      year = {2014},
      volume = {16},
      pages = {13191-13208},
      doi = {http://dx.doi.org/10.1039/C3CP54319F}
    }
    
    Jie Chen, Xue-Feng Wang, Panagiotis Vasilopoulos, An-Bang Chen & Jian-Chun Wu Single and Multiple Doping Effects on Charge Transport in Zigzag Silicene Nanoribbons 2014 ChemPhysChem
    Vol. 15(13), 2701-2706 
    DOI  
    Abstract: A non-equilibrium Green's function technique combined with density functional theory is used to study the spin-dependent electronic band structure and transport properties of zigzag silicene nanoribbons (ZSiNRs) doped with aluminum (Al) or phosphorus (P) atoms. The presence of a single Al or P atom induces quasibound states in ZSiNRs that can be observed as new dips in the electron conductance. The Al atom acts as an acceptor whereas the P atom acts as a donor if it is placed at the center of the ribbon. This behavior is reversed if the dopant is placed on the edges. Accordingly, an acceptor-donor transition is observed in ZSiNRs upon changing the dopant's position. Similar results are obtained if two silicon atoms are replaced by two impurities (Al or P atoms) but the conductance is generally modified due to the impurity-impurity interaction. If the doping breaks the twofold rotational symmetry about the central line, the transport becomes spin-dependent.
    Keywords: conductance, doping, electronic structure, nanoribbon, ATK, application, silicene
    Area: graphene, spin
    BibTeX:
    @article{Chen2014a,
      author = {Chen, Jie and Wang, Xue-Feng and Vasilopoulos, Panagiotis and Chen, An-Bang and Wu, Jian-Chun},
      title = {Single and Multiple Doping Effects on Charge Transport in Zigzag Silicene Nanoribbons},
      journal = {ChemPhysChem},
      publisher = {WILEY-VCH Verlag},
      year = {2014},
      volume = {15},
      number = {13},
      pages = {2701--2706},
      doi = {http://dx.doi.org/10.1002/cphc.201402171}
    }
    
    R.K. Ghosh, M. Brahma & S. Mahapatra Germanane: A Low Effective Mass and High Bandgap 2-D Channel Material for Future FETs 2014 IEEE Transactions on Electron Devices
    Vol. 61(7), 2309-2315 
    DOI  
    Abstract: We investigate the electronic properties of Germanane and analyze its importance as 2-D channel material in switching devices. Considering two types of morphologies, namely, chair and boat, we study the real band structure, the effective mass variation, and the complex band structure of unstrained Germanane by density-functional theory. The chair morphology turns out to be a more effective channel material for switching devices than the boat morphology. Furthermore, we study the effect of elastic strain, van der Waals force, and vertical electric field on these band structure properties. Due to its very low effective mass with relatively high-energy bandgap, in comparison with the other 2-D materials, Germanane appears to provide superior performance in switching device applications.
    Keywords: density functional theory;energy gap;field effect transistors;tunnel transistors;TFET;boat morphology;chair morphology;complex band structure;density-functional theory;elastic strain effect;electronic properties;high bandgap 2D channel material;high-energy bandgap;low effective mass;switching devices;tunnel field-effect transistor;unstrained germanane;Boats;Effective mass;Materials;Morphology;Photonic band gap;Tensile strain;2-D crystal;MOSFET;ab initio simulation;effective mass;real and complex band structure;tunnel field-effect transistor (TFET);tunnel field-effect transistor (TFET); ATK; Application
    Area: graphene, semi
    BibTeX:
    @article{Ghosh2014b,
      author = {Ghosh, R.K. and Brahma, M. and Mahapatra, S.},
      title = {Germanane: A Low Effective Mass and High Bandgap 2-D Channel Material for Future FETs},
      journal = {IEEE Transactions on Electron Devices},
      year = {2014},
      volume = {61},
      number = {7},
      pages = {2309-2315},
      doi = {http://dx.doi.org/10.1109/TED.2014.2325136}
    }
    
    Yuanyuan He, Jinjiang Zhang, Hongmei Liu & Jianwei Zhao Electron transport across pi-stacked oligophenyls system: A density functional theory approach 2014 Computational and Theoretical Chemistry
    Vol. 1043, 47 - 53 
    DOI  
    Abstract: To understand the pi-pi stacking interaction between layers of graphenes or polymers, parallel oligophenyls with pi-stacked units have been studied with non-equilibrium Green's function formalism and first-principle density functional theory from two aspects. With the increasing number of pi-stacked units, the pi-pi stacking interaction between parallel oligophenyl chains is enhanced whereas the coupling between the central molecules and the electrodes is weakened. The two effects reach a balance in the parallel oligophenyls with 5 pi-stacked units. The pi-pi stacking interaction is weakened exponentially with the separating distance. Large separating distance impedes electrons to pass through parallel molecules. These results provide a fundamental discussion on issues related to conjugated polymers and, in particular, organic semiconductor thin film devices.
    Keywords: Parallel oligophenyl, p-Stacked unit, Separating distance, Electron transport, pi-pi stacking interaction, ATK, Application
    Area: graphene
    BibTeX:
    @article{He2014,
      author = {Yuanyuan He and Jinjiang Zhang and Hongmei Liu and Jianwei Zhao},
      title = {Electron transport across pi-stacked oligophenyls system: A density functional theory approach},
      journal = {Computational and Theoretical Chemistry},
      year = {2014},
      volume = {1043},
      pages = {47 - 53},
      doi = {http://dx.doi.org/10.1016/j.comptc.2014.05.015}
    }
    
    Yuan yuan He & Jian wei Zhao Effects of Conformational Transformations on Electronic Transport Properties of Optical Molecular Switches: An ab initio Study 2014 Journal of Electrochemistry
    Vol. 20(3), 243-259 
    DOI  
    Abstract: A series of model molecules with 4 kinds of conformational transformations have been investigated as optical molecular switches by using density functional theory combined with nonequilibrium Green's function method. The theoretical calculations show that molecules after conformational transformations have photoswitching characteristics. We find that the photochromic molecules with the same conformational transformation usually have a similar current on/off state when they are applied as photoshwitches. Among these transformations, the molecular switch with E("trans")/Z("cis")-isomerisation of the NN double bond has the highest current on-off ratio. The influences of the energy gap (HLG) between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), spatial distributions, transmission and projected density of states (PDOS) spectra on the electronic transport through the optical molecular switches are discussed in detail.
    Keywords: ATK, Application, molecular switch, conformational transformations
    Area: molecular electronics
    BibTeX:
    @article{He2014c,
      author = {He, Yuan-yuan and Zhao, Jian-wei},
      title = {Effects of Conformational Transformations on Electronic Transport Properties of Optical Molecular Switches: An ab initio Study},
      journal = {Journal of Electrochemistry},
      year = {2014},
      volume = {20},
      number = {3},
      pages = {243-259},
      doi = {http://dx.doi.org/10.13208/j.electrochem.130881}
    }
    
    Faruque M. Hossain, Feras Al-Dirini & Efstratios Skafidas A graphene nanoribbon neuro-sensor for glycine detection and imaging 2014 Journal of Applied Physics
    Vol. 115(21), 214303 
    DOI  
    Abstract: Glycine acts as a neurotransmitter in the Central Nervous System (CNS) and plays a vital role in processing of motor and sensory information that control movement, vision, and audition. Glycine detection and imaging can lead to a greater understanding of how this information is processed in the CNS. Here, we present a neuro-sensor for the detection and imaging of Glycine molecules, based on a zigzag Graphene Nanoribbon device structure. An energetically stable Nitrogen Vacancy (NV) center is introduced in the device to enable its use in neuronal imaging applications.We demonstrate, by using the Density Functional Theory and Nonequilibrium Green's Function method, that the device detects the attachment of a single Glycine molecule to its edges by significant changes in its conductance. The attachment of Glycine induces current channels around the NV center increasing the current flow through the device. In absence of Glycine, the presence of the NV center suppresses current flow through the device, significantly reducing its power consumption, and allowing for its use in proximity of living neuron cells.
    Keywords: ATK, Application, graphene, nanoribbon, glycine, sensor
    Area: graphene
    BibTeX:
    @article{Hossain2014,
      author = {Hossain, Faruque M. and Al-Dirini, Feras and Skafidas, Efstratios},
      title = {A graphene nanoribbon neuro-sensor for glycine detection and imaging},
      journal = {Journal of Applied Physics},
      year = {2014},
      volume = {115},
      number = {21},
      pages = {214303},
      doi = {http://dx.doi.org/10.1063/1.4880744}
    }
    
    Brahmanandam Javvaji, Abhilash Ravikumar, B.M. Shenoy, D. Roy Mahapatra, M.R. Rahman & G.M. Hegde Electronic band structure and photoemission spectra of graphene on silicon substrate 2014 Proceedings of SPIE
    Vol. 7 
    DOI  
    Abstract: Synergizing graphene on silicon based nanostructures is pivotal in advancing nano-electronic device technology. A combination of molecular dynamics and density functional theory has been used to predict the electronic energy band structure and photo-emission spectrum for graphene-Si system with silicon as a substrate for graphene. The equilibrium geometry of the system after energy minimization is obtained from molecular dynamics simulations. For the stable geometry obtained, density functional theory calculations are employed to determine the energy band structure and dielectric constant of the system. Further the work function of the system which is a direct consequence of photoemission spectrum is calculated from the energy band structure using random phase approximations.
    Keywords: ATK, Application
    Area: graphene
    BibTeX:
    @article{Javvaji2014,
      author = {Brahmanandam Javvaji and Abhilash Ravikumar and B. M. Shenoy and D. Roy Mahapatra and M. R. Rahman and G. M. Hegde},
      title = {Electronic band structure and photoemission spectra of graphene on silicon substrate},
      journal = {Proceedings of SPIE},
      year = {2014},
      volume = {7},
      doi = {http://dx.doi.org/10.1117/12.2042576}
    }
    
    Yu-Shen Liu, Xue Zhang, Jin-Fu Feng & Xue-Feng Wang Spin-resolved Fano resonances induced large spin Seebeck effects in graphene-carbon-chain junctions 2014 Applied Physics Letters
    Vol. 104(24), - 
    DOI  
    Abstract: We propose a high-efficiency thermospin device constructed by a carbon atomic chain sandwiched between two ferromagnetic (FM) zigzag graphene nanoribbon electrodes. In the low-temperature regime, the magnitude of the spin figure of merit is nearly equal to that of the corresponding charge figure of merit. This is attributed to the appearances of spin-resolved Fano resonances in the linear conductance spectrum resulting from the quantum interference effects between the localized states and the expanded states. The spin-dependent Seebeck effect is obviously enhanced near these Fano resonances with the same spin index; meanwhile, the Seebeck effect of the other spin component has a smaller value due to the smooth changing of the linear conductance with the spin index. Thus, a large spin Seebeck effect is achieved, and the magnitude of the spin figure of merit can reach 1.2 at T=25 K. Our results indicate that the FM graphene-carbon-chain junctions can be used to design the high-efficiency thermospin devices.
    Keywords: ATK, Application, Seebeck, Fano resonance
    Area: graphene, thermo, spin
    BibTeX:
    @article{Liu2014a,
      author = {Liu, Yu-Shen and Zhang, Xue and Feng, Jin-Fu and Wang, Xue-Feng},
      title = {Spin-resolved Fano resonances induced large spin Seebeck effects in graphene-carbon-chain junctions},
      journal = {Applied Physics Letters},
      year = {2014},
      volume = {104},
      number = {24},
      pages = {-},
      doi = {http://dx.doi.org/10.1063/1.4884424}
    }
    
    N. Liu, J.B. Liu, G.Y. Gao & K.L. Yao Carbon doping induced giant low bias negative differential resistance in boron nitride nanoribbon 2014 Physics Letters A
    Vol. 378(30-31), 2217 - 2221 
    DOI  
    Abstract: By applying nonequilibrium Green's function combined with density functional theory, we investigated the electronic transport properties of carbon-doped armchair boron nitride nanoribbons. Obvious negative differential resistance (NDR) behavior with giant peak-to-valley ratio up to the order of 10^4 - 10^6 is found by tuning the doping position and concentration. Especially, with the reduction of doping concentration, NDR peak position can enter into mV bias range and even can be expected lower than mV bias. The negative differential resistance behavior is explained by the evolution of the transmission spectra and band structures with applied bias.
    Keywords: Boron nitride, Electronic transport properties, Negative differential resistance, ATK, Application
    Area: graphene
    BibTeX:
    @article{Liu2014d,
      author = {N. Liu and J.B. Liu and G.Y. Gao and K.L. Yao},
      title = {Carbon doping induced giant low bias negative differential resistance in boron nitride nanoribbon},
      journal = {Physics Letters A},
      year = {2014},
      volume = {378},
      number = {30-31},
      pages = {2217 - 2221},
      doi = {http://dx.doi.org/10.1016/j.physleta.2014.06.020}
    }
    
    M.A. Mehrabova, I.R. Nuriyev & H.S. Orujov Electron structure and optical properties of Cd1-XMnXTe thin films 2014 INTERNATIONAL JOURNAL OF MATERIALS
    Vol. 1, 63-70 
    URL 
    Abstract: Band structure and DOS have been calculated for Cd1-xMnxTe (x=0.0625, x=0.0312, x=0.0156) semimagnetic semiconductors by ab-initio method using the Atomistix Toolkit program. It has been determined that with an increase in Mn quantity, the energy gap increases and lattice parameter decreases. The calculated magnetic moment for Mn atom is found to be equal to 5 uB. It was revealed that the antiferromagnetic phase is stable in Cd1-xMnxTe. The theoretical results are in good agreement with the experimental data obtained by us. It has been synthesized Cd1-xMnxTe solid solutions (x=0.01, 0.03, 0.05). Thin films of the given solid solutions were obtained on the glass and mica substrates. Lattice parameters and compositions of the obtained samples were defined with X-ray diffraction method. It has been defined the optimum conditions for obtaining of Cd1-xMnxTe (x=0.01, 0.03, 0.05) solid solutions' thin films on the glass and mica substrates. With increasing of substrate temperature, films obtained on the glass substrates are crystallized, and the films obtained on the mica substrates became more perfect. The homogeneity of the composition of synthesized solid solutions have been established by EPR method.
    Keywords: semimagnetic semiconductor, molecular beam condensation, X-ray diffraction method, UVS, ATK, Application
    Area: semi, spin
    BibTeX:
    @article{Mehrabova2014,
      author = {M. A. Mehrabova and I. R. Nuriyev and H. S. Orujov},
      title = {Electron structure and optical properties of Cd1-XMnXTe thin films},
      journal = {INTERNATIONAL JOURNAL OF MATERIALS},
      year = {2014},
      volume = {1},
      pages = {63-70},
      url = {http://www.naun.org/main/NAUN/materials/2014/a122005-184.pdf}
    }
    
    Li Peng, Kailun Yao, Sicong Zhu, Yun Ni, Fengxia Zu, Shuling Wang, Bin Guo & Yong Tian Spin transport properties of partially edge-hydrogenated MoS2 nanoribbon heterostructure 2014 Journal of Applied Physics
    Vol. 115(22), 223705 
    DOI  
    Abstract: We report ab initio calculations of electronic transport properties of heterostructure based on MoS2 nanoribbons. The heterostructure consists of edge hydrogen-passivated and non-passivated zigzag MoS2 nanoribbons (ZMoS2NR-H/ZMoS2NR). Our calculations show that the heterostructure has half-metallic behavior which is independent of the nanoribbon width. The opening of spin channels of the heterostructure depends on the matching of particular electronic orbitals in the Mo-dominated edges of ZMoS2NR-H and ZMoS2NR. Perfect spin filter effect appears at small bias voltages, and large negative differential resistance and rectifying effects are also observed in the heterostructure.
    Keywords: atk, application, spin transport, MoS2, nanoribbon, heterostructure
    Area: 2dmat, tmd
    BibTeX:
    @article{Peng2014b,
      author = {Peng, Li and Yao, Kailun and Zhu, Sicong and Ni, Yun and Zu, Fengxia and Wang, Shuling and Guo, Bin and Tian, Yong},
      title = {Spin transport properties of partially edge-hydrogenated MoS2 nanoribbon heterostructure},
      journal = {Journal of Applied Physics},
      year = {2014},
      volume = {115},
      number = {22},
      pages = {223705},
      doi = {http://dx.doi.org/10.1063/1.4882195}
    }
    
    Maharavo Randrianarivony On DFT Molecular Simulation for Non-Adaptive Kernel Approximation 2014 Advances in Materials Physics and Chemistry
    Vol. 04(06), 105-115 
    DOI  
    Abstract: Using accurate quantum energy computations in nanotechnologic applications is usually very computationally intensive. That makes it difficult to apply in subsequent quantum simulation. In this paper, we present some preliminary results pertaining to stochastic methods for alleviating the numerical expense of quantum estimations. The initial information about the quantum energy originates from the Density Functional Theory. The determination of the parameters is performed by using methods stemming from machine learning. We survey the covariance method using marginal likelihood for the statistical simulation. More emphasis is put at the position of equilibrium where the total atomic energy attains its minimum. The originally intensive data can be reproduced efficiently without losing accuracy. A significant acceleration gain is perceived by using the proposed method.
    Keywords: ATK, Application, DFT, Energy, Stochastic, Covariance, Hyperparameter, molecules
    Area: materials
    BibTeX:
    @article{Randrianarivony2014,
      author = {Randrianarivony, Maharavo},
      title = {On DFT Molecular Simulation for Non-Adaptive Kernel Approximation},
      journal = {Advances in Materials Physics and Chemistry},
      publisher = {Scientific Research Publishing, Inc,},
      year = {2014},
      volume = {04},
      number = {06},
      pages = {105-115},
      doi = {http://dx.doi.org/10.4236/ampc.2014.46013}
    }
    
    S.J. Ray Single Atom Impurity in a Single Molecular Transistor 2014   URL 
    Abstract: The influence of an impurity atom on the electrostatic behaviour of a Single Molecular Transistor (SMT) was investigated through Ab-initio calculations in a double-gated geometry. The charge stability diagram carries unique signature of the position of the impurity atom in such devices which together with the charging energy of the molecule could be utilised as an electronic fingerprint for the detection of such impurity states in a nano-electronic device. The two gated geometry allows additional control over the electrostatics as can be seen from the total energy surfaces (for a specific charge state) which is sensitive to the positions of the impurity. These devices which are operational at room temperature can provide significant advantages over the conventional Silicon based single dopant devices functional at low temperature. The present approach could be a very powerful tool for the detection and control of individual impurity atoms in a single molecular device and for applications in future molecular electronics.
    Keywords: ATK, application, single molecule transistor
    Area: molecular electronics
    BibTeX:
    @article{Ray2014a,
      author = {S. J. Ray},
      title = {Single Atom Impurity in a Single Molecular Transistor},
      year = {2014},
      url = {http://arxiv.org/abs/1406.0170}
    }
    
    S. Sivasathya, D. John Thiruvadigal & S. Mathi Jaya Electron transport through metallic single wall carbon nanotubes with adsorbed NO2 and NH3 molecules: A first-principles study 2014 Chemical Physics Letters
    Vol. 609, 76 - 81 
    DOI  
    Abstract: In this Letter, variations in the transport characteristics of metallic single wall carbon nanotubes (SWCNTs) due to the absorption of NO2 and NH3 molecules on the surface are investigated using the Landauer formalism combined with the non-equilibrium Green's function techniques and ab initio electronic structure obtained using density functional theory (DFT). The electronic structure, charge distribution, transmission spectrum and I-V characteristics of the SWCNT are significantly changed on adsorption which is reflected in the conductance and transport characteristics of the SWCNT. Thus, we conclude that these systems can be used in CNT based NO2 and NH3 gas sensors.
    Keywords: ATK, Application, carbon nanotube, NO2, NH3, electron transport
    Area: nanotubes
    BibTeX:
    @article{Sivasathya2014,
      author = {S. Sivasathya and D. John Thiruvadigal and S. Mathi Jaya},
      title = {Electron transport through metallic single wall carbon nanotubes with adsorbed NO2 and NH3 molecules: A first-principles study},
      journal = {Chemical Physics Letters},
      year = {2014},
      volume = {609},
      pages = {76 - 81},
      doi = {http://dx.doi.org/10.1016/j.cplett.2014.06.038}
    }
    
    Pankaj Srivastava, Neeraj K. Jaiswal & Varun Sharma First-principles investigation of armchair boron nitride nanoribbons for sensing PH3 gas molecules 2014 Superlattices and Microstructures
    Vol. 73, 350 - 358 
    DOI  
    Abstract: The present work exhibits density functional theory (DFT) based first-principles calculations to explore the sensing properties of bare armchair boron nitride nanoribbons (ABNNR) for PH3 gas molecules. Edges of the ribbon were considered as the sites of possible adsorption with two different configurations i.e. adsorption at one edge and adsorption at both edges of the ribbon. It is revealed that B atoms of the ribbons are more energetically favorable sites for the adsorption of PH3 molecules as compared with N atoms. The adsorption of PH3 affects the electronic properties of nanoribbons. One edge PH3 adsorbed ribbons are metallic whereas in both edges PH3 adsorption, the band gap is decreased than that of bare ribbon. The changes in electronic properties caused by PH3 adsorption are further supported by the current-voltage (I-V) characteristics of the considered configurations. The results show that ABNNR can serve as a potential candidate for PH3 sensing applications.
    Keywords: Nanoribbons, Band structures, Density of states, I-V characteristics, Sensors, ATK, application
    Area: graphene
    BibTeX:
    @article{Srivastava2014e,
      author = {Pankaj Srivastava and Neeraj K. Jaiswal and Varun Sharma},
      title = {First-principles investigation of armchair boron nitride nanoribbons for sensing PH3 gas molecules},
      journal = {Superlattices and Microstructures },
      year = {2014},
      volume = {73},
      pages = {350 - 358},
      doi = {http://dx.doi.org/10.1016/j.spmi.2014.05.036}
    }
    
    Zhongbo Su, Yipeng An, Xinyuan Wei & Zhongqin Yang Spin-dependent thermoelectronic transport of a single molecule magnet Mn(dmit)2 2014 Journal of Chemical Physics
    Vol. 140(20), 204707 
    DOI  
    Abstract: We investigate spin-dependent thermoelectronic transport properties of a single molecule magnet Mn(dmit)2 sandwiched between two Au electrodes using first-principles density functional theory combined with nonequilibrium Green's function method. By applying a temperature difference between the two Au electrodes, spin-up and spin-down currents flowing in opposite directions can be induced due to asymmetric distribution of the spin-up and spin-down transmission spectra around the Fermi level. A pure spin current and 100% spin polarization are achieved by tuning backgate voltage to the system. The spin caloritronics of the molecule with a perpendicular conformation is also explored, where the spin-down current is blocked strongly. These results suggest that Mn(dmit)2 is a promising material for spin caloritronic applications.
    Keywords: ATK, Application, thermoelectric transport, single molecule magnet
    Area: molecular electronics, spin, thermo
    BibTeX:
    @article{Su2014,
      author = {Su, Zhongbo and An, Yipeng and Wei, Xinyuan and Yang, Zhongqin},
      title = {Spin-dependent thermoelectronic transport of a single molecule magnet Mn(dmit)2},
      journal = {Journal of Chemical Physics},
      publisher = {AIP Publishing},
      year = {2014},
      volume = {140},
      number = {20},
      pages = {204707},
      doi = {http://dx.doi.org/10.1063/1.4879056}
    }
    
    Qiu-Hua Wu, Peng Zhao, Hai-Ying Liu, Yan Su, De-Sheng Liu & Gang Chen Low-bias negative differential resistance in combined nanostructure of two zigzag-edged trigonal graphenes 2014 Physics Letters A
    Vol. 378(30-31), 2191 - 2194 
    DOI  
    Abstract: Using the density functional theory combined with the non-equilibrium Green's function method, we have investigated the electron transport properties of combined nanostructures of two zigzag-edged trigonal graphenes linked by their vertex carbon atoms bridged between two gold electrodes. The results show that obvious negative differential resistance behavior can be obtained at low bias (0.3 V) in such combined systems. The observed low-bias negative differential resistance behavior is analyzed by the bias-dependent transmission spectra, projected density of states, and voltage drop.
    Keywords: Negative differential resistance, Zigzag-edged trigonal graphene, Density functional theory, Non-equilibrium Greens function, ATK, Application
    Area: graphene
    BibTeX:
    @article{Wu2014f,
      author = {Qiu-Hua Wu and Peng Zhao and Hai-Ying Liu and Yan Su and De-Sheng Liu and Gang Chen},
      title = {Low-bias negative differential resistance in combined nanostructure of two zigzag-edged trigonal graphenes},
      journal = {Physics Letters A },
      year = {2014},
      volume = {378},
      number = {30-31},
      pages = {2191 - 2194},
      doi = {http://dx.doi.org/10.1016/j.physleta.2014.05.029}
    }
    
    Bo Xiao, Xuefang Yu, Hong Hu & Yihong Ding Beryllium decorated armchair boron nitride nanoribbon: A new planar tetracoordinate nitride containing system with enhanced conductivity 2014 Chemical Physics Letters
    Vol. 608, 277 - 283 
    DOI  
    Abstract: Abstract In this Letter, a new kind of planar tetracoordinate nitride (ptN) structure is obtained via Be-decorated armchair boron nitride nanoribbon (aBNNR). The high stability of such a ptN system is confirmed by both global minimization and molecular dynamical simulation at 1500 K. The results suggest that this Be-decorated aBNNR will be a thermally stable material. The electronic property of aBNNR is significantly increased after the addition of Be atoms to the edges and the band gap decreases as the width of the ribbon decreases. Our Letter posits a new and potentially stable and useful BNNR and augments the literature on ptN.
    Keywords: ATK, Application, boron nitride nanoribbon, beryllium, conductivity
    Area: graphene
    BibTeX:
    @article{Xiao2014b,
      author = {Bo Xiao and Xuefang Yu and Hong Hu and Yihong Ding},
      title = {Beryllium decorated armchair boron nitride nanoribbon: A new planar tetracoordinate nitride containing system with enhanced conductivity},
      journal = {Chemical Physics Letters },
      year = {2014},
      volume = {608},
      pages = {277 - 283},
      doi = {http://dx.doi.org/10.1016/j.cplett.2014.05.095}
    }
    
    Jing Zeng, Liezun Chen & Ke-Qiu Chen Improving spin-filtering efficiency in graphene and boron nitride nanoribbon heterostructure decorated with chromium-ligand 2014 Organic Electronics
    Vol. 15(5), 1012 - 1017 
    DOI  
    Abstract: By applying nonequilibrium Green's functions in combination with density-function theory, we investigate the spin-dependent transport properties of graphene and boron nitride nanoribbon heterostructure decorated with chromium-ligand. In the heterostructure, the graphene and boron nitride nanoribbon are connected in a interlaced way, and the chromium-ligand are decorated above the surface of the graphene nanoribbon. When one boron nitride nanoribbon fragment is embedded in the graphene nanoribbon, the maximum spin-filtering efficiency at finite bias is only about 65%. However, almost 100% spin-filtering efficiency can be observed at low bias when one more BNNR fragment is introduced into the system. Especially, the high spin-filtering efficiency is independent of the magnetic configuration of the device. Our work provides a new thinking to achieve the high-performance spin filter.
    Keywords: Spin transport in nanoscale materials and structures, Spin-filtering effect, Molecular magnets, ATK, application
    Area: spintronics
    BibTeX:
    @article{Zeng2014b,
      author = {Jing Zeng and Liezun Chen and Ke-Qiu Chen},
      title = {Improving spin-filtering efficiency in graphene and boron nitride nanoribbon heterostructure decorated with chromium-ligand},
      journal = {Organic Electronics },
      year = {2014},
      volume = {15},
      number = {5},
      pages = {1012 - 1017},
      doi = {http://dx.doi.org/10.1016/j.orgel.2014.02.010}
    }
    
    J.J. Zhang, Z.H. Zhang, G.P. Tang, X.Q. Deng & Z.Q. Fan Modulating magnetic ordering of the zigzag-edge trigonal graphene by functionalizations 2014 Organic Electronics
    Vol. 15(7), 1338 - 1346 
    DOI  
    Abstract: A pristine zigzag-edge trigonal graphene (ZTG) is a magnetic semiconductor, thus its spin polarization is extremely low. Here, we report the calculated results on enhancing the spin magnetism of a zigzag-edge trigonal graphene (ZTG) by functionalizations, including the heteroatom doping, edge modifications, and introducing topologic defects. It is found that the ZTG features a good tuning ability for functionalizations to improve its spin polarization. When one boron (B) atom is doped to replace one carbon atom in the B sublattice of graphene, a higher spin polarization can be achieved, and the edge modification by Cu, Co, O or B atom can modulate the magnetic ordering significantly due to the spin-polarized charge transfer between the ZTG and terminations, especially for O and Co terminations. And also, the introduced defect (a vacancy and a Stone-Wales defect) can obviously tune local magnetic structures owing to geometrically structural deformations (variations of bond length and bond angle). For these behaviors, in-depth analyses are performed. Our findings suggest that the desirable functionalized ZTG structures might promise importantly potential applications for developing nano-scale spintronics devices.
    Keywords: Functionalization, Spin polarization, Local magnetic structure, Trigonal graphene, ATK, application
    Area: graphene
    BibTeX:
    @article{Zhang2014d,
      author = {J.J. Zhang and Z.H. Zhang and G.P. Tang and X.Q. Deng and Z.Q. Fan},
      title = {Modulating magnetic ordering of the zigzag-edge trigonal graphene by functionalizations},
      journal = {Organic Electronics },
      year = {2014},
      volume = {15},
      number = {7},
      pages = {1338 - 1346},
      doi = {http://dx.doi.org/10.1016/j.orgel.2014.03.036}
    }
    
    Ye Zhang, Yuee Xie, Tao Ouyang & Yuanping Chen Resonant transport and negative differential resistance in the graphene and graphyne quantum dots 2014 Physica B: Condensed Matter
    Vol. 445, 88 - 92 
    DOI  
    Abstract: The electronic transport properties of graphene and graphyne quantum dots embedded in zigzag-edged graphene nanoribbons are studied. The results show that the quasi-bound states in the quantum dots induce resonant transmission around the Fermi level in the transmission spectrums. While the resonant peaks lead to robust negative differential resistance (NDR) behaviors. Moreover, the resonant transmission and NDR behavior are very sensitive to the size of the quantum dots. As the size of quantum dots increases, the number of resonant peaks increases and shift to the Fermi level, correspondingly the NDR phenomena shift to lower bias. Compared with graphene quantum dots, graphyne quantum dots show more amazing transport properties. These interesting findings could offer useful guidelines for the design of electronics associated with resonant and NDR phenomenon.
    Keywords: Graphene quantum dots, Graphyne quantum dots, NDR, Resonant transmissions, ATK, application
    Area: graphene
    BibTeX:
    @article{Zhang2014e,
      author = {Ye Zhang and Yuee Xie and Tao Ouyang and Yuanping Chen},
      title = {Resonant transport and negative differential resistance in the graphene and graphyne quantum dots},
      journal = {Physica B: Condensed Matter },
      year = {2014},
      volume = {445},
      pages = {88 - 92},
      doi = {http://dx.doi.org/10.1016/j.physb.2014.03.020}
    }
    
    Zhi-Qiang Fan, Zhen-Hua Zhang, Xiao-Qing Deng, Gui-Ping Tang, Hua-Li Zhu, Yun Ren & Fang Xie Structural, electronic, and transport properties of Ih-symmetry-breaking C60 isomers 2014 Computational Materials Science
    Vol. 91, 15 - 19 
    DOI  
    Abstract: Using the non-equilibrium Green's function method combined with the density functional theory, the structural, electronic, and transport properties of Ih-symmetry-breaking C60 isomers are investigated. The results show that the Stone-Wales rearrangement not only changes the geometry of C60 molecule but also modulates the arrangement of its frontier molecular orbitals effectively. When the molecule is sandwiched between two gold electrodes as a molecular device, the Stone-Wales rearrangement can always enhance the device's electronic transport ability whatever the pristine or the B-doped C60 molecule. The mechanisms are proposed for these phenomena.
    Keywords: C60, Stone-Wales, ATK, Application
    Area: molecular electronics
    BibTeX:
    @article{Fan2014,
      author = {Zhi-Qiang Fan and Zhen-Hua Zhang and Xiao-Qing Deng and Gui-Ping Tang and Hua-Li Zhu and Yun Ren and Fang Xie},
      title = {Structural, electronic, and transport properties of Ih-symmetry-breaking C60 isomers},
      journal = {Computational Materials Science },
      year = {2014},
      volume = {91},
      pages = {15 - 19},
      doi = {http://dx.doi.org/10.1016/j.commatsci.2014.04.013}
    }
    
    Qun Gao & Jing Guo Role of chemical termination in edge contact to graphene 2014 APL Materials
    Vol. 2(5), 056105 
    DOI  
    Abstract: Edge contacts to graphene can offer excellent contact properties. Role of different chemical terminations is examined by using ab initio density functional theory and quantum transport simulations. It is found that edge termination by group VI elements O and S offers considerably lower contact resistance compared to H and group VII element F. The results can be understood by significantly larger binding energy and shorter binding distance between the metal contact and these group VI elements, which results in considerably lower interface potential barrier and larger transmission. The qualitative conclusion applies to a variety of contact metal materials.
    Keywords: ATK, Application, graphene, edge termination, contact resistance
    Area: graphene
    BibTeX:
    @article{Gao2014a,
      author = {Gao, Qun and Guo, Jing},
      title = {Role of chemical termination in edge contact to graphene},
      journal = {APL Materials},
      year = {2014},
      volume = {2},
      number = {5},
      pages = {056105},
      doi = {http://dx.doi.org/10.1063/1.4876635}
    }
    
    Ganesh Hegde, Michael Povolotskyi, Tillmann Kubis, Timothy Boykin & Gerhard Klimeck An environment-dependent semi-empirical tight binding model suitable for electron transport in bulk metals, metal alloys, metallic interfaces, and metallic nanostructures. I. Model and validation 2014 Journal of Applied Physics
    Vol. 115(12), 123703 
    DOI  
    Abstract: Semi-empirical Tight Binding (TB) is known to be a scalable and accurate atomistic representation for electron transport for realistically extended nano-scaled semiconductor devices that might contain millions of atoms. In this paper, an environment-aware and transferable TB model suitable for electronic structure and transport simulations in technologically relevant metals, metallic alloys, metal nanostructures, and metallic interface systems are described. Part I of this paper describes the development and validation of the new TB model. The new model incorporates intraatomic diagonal and off-diagonal elements for implicit self-consistency and greater transferability across bonding environments. The dependence of the on-site energies on strain has been obtained by appealing to the Moments Theorem that links closed electron paths in the system to energy moments of angular momentum resolved local density of states obtained ab initio. The model matches self-consistent density functional theory electronic structure results for bulk face centered cubic metals with and without strain, metallic alloys, metallic interfaces, and metallic nanostructures with high accuracy and can be used in predictive electronic structure and transport problems in metallic systems at realistically extended length scales.
    Keywords: ATK-SE, Application, tight binding, electron transport
    Area: semi
    BibTeX:
    @article{Hegde2014a,
      author = {Hegde, Ganesh and Povolotskyi, Michael and Kubis, Tillmann and Boykin, Timothy and Klimeck, Gerhard},
      title = {An environment-dependent semi-empirical tight binding model suitable for electron transport in bulk metals, metal alloys, metallic interfaces, and metallic nanostructures. I. Model and validation},
      journal = {Journal of Applied Physics},
      year = {2014},
      volume = {115},
      number = {12},
      pages = {123703},
      doi = {http://dx.doi.org/10.1063/1.4868977}
    }
    
    Jianming Jia, Daning Shi, Xiaoqin Feng & Guibin Chen Electromechanical properties of armchair graphene nanoribbons under local torsion 2014 Carbon
    Vol. 76, 54 - 63 
    DOI  
    Abstract: While graphene nanoribbons are prone to twist intrinsically, the effect of local twist on the electromechanical properties remains unexplored. By using the density functional theory in combination with the nonequilibrium Green's function method, we investigate the responses of structural evolution and electrical transport of armchair graphene nanoribbons to local torsion. We show that local twist can alter their transport properties significantly. The current at a given bias can switch on/off or change many times with twist angle, which is related with twist-induced changes in electronic structures of graphene nanoribbons. Our results can provide a valuable guideline for design and implementation of graphene nanoribbons in nanoelectromechanical systems and devices.
    Keywords: ATK, Application, graphene, nanoribbon, torsion
    Area: graphene
    BibTeX:
    @article{Jia2014,
      author = {Jianming Jia and Daning Shi and Xiaoqin Feng and Guibin Chen},
      title = {Electromechanical properties of armchair graphene nanoribbons under local torsion},
      journal = {Carbon},
      year = {2014},
      volume = {76},
      pages = {54 - 63},
      doi = {http://dx.doi.org/10.1016/j.carbon.2014.04.048}
    }
    
    Vladimir Kolchuzhin, Jan Mehner, Erik Markert, Ulrich Heinkel, Christian Wagner, Jorg Schuster & Thomas Gessner System-level-model development of an SWCNT based piezoresistive sensor in VHDL-AMS 2014 15th international conference on Thermal, mechanical and multi-physics simulation and experiments in microelectronics and microsystems (eurosime), 1-6  DOI  
    Abstract: This article deals with the model development for a single walled carbon nanotube (SWCNT) piezoresistive sensor at system level design. The framework of VHDLAMS is used for implementation and simulation, consisting of compact submodels that describe components performing heterogeneous functions. The SWCNT mechanical and electrical compact models presented in the article are based on the analytical model, lumped element model and the simulation results based on density functional theory (DFT). The macromodels of the MEMS are built using a reduced order modeling technique based on finite element simulations. This article presents and discusses the most important aspects of the development of system models and essential model parameters.
    Keywords: ATK, Application
    Area: nanotubes
    BibTeX:
    @inproceedings{Kolchuzhin2014,
      author = {Vladimir Kolchuzhin and Jan Mehner and Erik Markert and Ulrich Heinkel and Christian Wagner and Jorg Schuster and Thomas Gessner},
      title = {System-level-model development of an SWCNT based piezoresistive sensor in VHDL-AMS},
      booktitle = {15th international conference on Thermal, mechanical and multi-physics simulation and experiments in microelectronics and microsystems (eurosime)},
      publisher = {IEEE},
      year = {2014},
      pages = {1-6},
      doi = {http://dx.doi.org/10.1109/EuroSimE.2014.6813846}
    }
    
    Silvio Osella, Victor Geskin, Jerome Cornil & David Beljonne Coherent Electron Transmission across Nanographenes Tethered to Gold Electrodes: Influence of Linker Topology, Ribbon Width, and Length 2014 The Journal of Physical Chemistry
    Vol. 118(14), 7643-7652 
    DOI  
    Abstract: The conductance of several well-defined and experimentally accessible graphene nanoribbons (GNRs) linked to gold electrodes by thiol groups to form single-molecule junctions is investigated within the nonequilibrium Green's function formalism coupled to density functional theory. We focus on the change in conduction as a function of the width and length of the ribbons as well as the number and position of the linking groups. The calculations illustrate that the position of the linkers is a key parameter controlling the conductance through the GNRs investigated here, as can be anticipated from their Clar sextet representations. The increase in width yields higher conductance only if accompanied by an increasing number of linkers due to the opening of additional pathways. The decay of transmission with GNR length is close to exponential, with rather low attenuation factors (0.06-0.11 Angstrom-1) that depend on the ribbon topology.
    Keywords: ATK, Application, graphene, nanoribbon, gold electrode, conductance, attenuation
    Area: graphene
    BibTeX:
    @article{Osella2014,
      author = {Osella, Silvio and Geskin, Victor and Cornil, Jerome and Beljonne, David},
      title = {Coherent Electron Transmission across Nanographenes Tethered to Gold Electrodes: Influence of Linker Topology, Ribbon Width, and Length},
      journal = {The Journal of Physical Chemistry},
      year = {2014},
      volume = {118},
      number = {14},
      pages = {7643-7652},
      doi = {http://dx.doi.org/10.1021/jp411572x}
    }
    
    Sweta Parashar, Pankaj Srivastava & Manisha Pattanaik Effect of electrode materials on transport properties of asymmetric biphenyl molecular junctions 2014 Solid State Communications
    Vol. 191, 54 - 58 
    DOI  
    Abstract: We analyze the effect of electrode materials Y (Y=Ag, Cu, and Pt) on electronic transport properties of asymmetric biphenyl molecular junctions using first-principles calculations. To introduce coupling asymmetry in these junctions, one end of the biphenyl molecule is terminated by conjugated double thiol (model A) and single thiol (model B) anchoring groups, while the other end is terminated by Cu atom. We reveal that, for Ag and Cu electrode, conjugated double thiol exhibit stronger rectifying performance in contrast to nonconjugated single thiol group. Further, when the molecule is connected to the Pt electrode through single thiol and Cu atom, multifunctional behavior with excellent rectifying performance and clear negative differential resistance (NDR) are observed for the first time. The present results will pave a new roadmap for designing functional molecular devices.
    Keywords: ATK, Application, molecular junction
    Area: molecular electronics
    BibTeX:
    @article{Parashar2014,
      author = {Sweta Parashar and Pankaj Srivastava and Manisha Pattanaik},
      title = {Effect of electrode materials on transport properties of asymmetric biphenyl molecular junctions },
      journal = {Solid State Communications },
      year = {2014},
      volume = {191},
      pages = {54 - 58},
      doi = {http://dx.doi.org/10.1016/j.ssc.2014.04.019}
    }
    
    S.J. Ray & R. Chowdhury Double Gated Single Molecular Transistor for Charge Detection 2014 Journal of Applied Physics
    Vol. 116, 034307 
    DOI  
    Abstract: The electrostatic behaviour of an 1,3-Cyclobutadiene (C4H4) based Single Molecular Transistor (SMT) has been investigated using the first principle calculation based on Density functional Theory and non-equilibrium Green's function approach. While the molecule is placed on top of a dielectric layer (backed by a metallic gate) and weakly coupled between the Source/Drain electrodes, the charge stability diagram revealed the presence of individual charge states in the Coulomb Blockade regime. This gets affected significantly on addition of an another gate electrode placed on the top of the molecule. This modified double-gated geometry allows additional control of the total energy of the system that is sensitive to the individual charge states of the molecule which can be used as a charge sensing technique operational at room temperature.
    Keywords: ATK, Application, molecular transistor, Coulomb blockade
    Area: molecular electronics
    BibTeX:
    @article{Ray2014b,
      author = {S. J. Ray and R. Chowdhury},
      title = {Double Gated Single Molecular Transistor for Charge Detection},
      journal = {Journal of Applied Physics},
      year = {2014},
      volume = {116},
      pages = {034307},
      doi = {http://dx.doi.org/10.1063/1.4890540}
    }
    
    Guiping Tang, Zhenhua Zhang, Xiaoqing Deng, Zhiqiang Fan, Yongchang Zeng & Jicheng Zhou Improved scaling rules for bandgaps in graphene nanomeshs 2014 Carbon
    Vol. 76, 348 - 356 
    DOI  
    Abstract: The ways to solve an outstanding problem on how to properly pattern graphene to induce bandgaps are reported, in particular, related altering regularities and mechanisms are investigated systematically. For the graphene nanomeshes (GNMs) with circular, triangular and rectangular holes, the respective new scaling rules to quantitatively reflect the relationship between the bandgap and the structural parameters of GNMs are proposed, which demonstrates a well applicability for a description of bandgaps of GNM with different size, shape, and density of hole. Furthermore, the underlying mechanisms for opening bandgap are revealed and the altering regularities of bandgaps are clearly explained.
    Keywords: ATK, Application, graphene, bandgap
    Area: graphene
    BibTeX:
    @article{Tang2014,
      author = {Guiping Tang and Zhenhua Zhang and Xiaoqing Deng and Zhiqiang Fan and Yongchang Zeng and Jicheng Zhou},
      title = {Improved scaling rules for bandgaps in graphene nanomeshs},
      journal = {Carbon },
      year = {2014},
      volume = {76},
      pages = {348 - 356},
      doi = {http://dx.doi.org/10.1016/j.carbon.2014.04.086}
    }
    
    Tingting Weng, Daniel DeBrincat, Vaida Arcisauskaite & John E. McGrady In search of structure-function relationships in transition-metal based rectifiers 2014 Inorg. Chem. Front.
    Vol. 1, 468-477 
    DOI  
    Abstract: Heterometallic chains have been proposed as potential current rectifiers in molecular electronics, their left-right asymmetry providing, at least in principle, a mechanism for differentiation of current flow in forward and reverse directions. Here we compare two known extended metal atom chains (EMACs), Ru2Ni(dpa)4(NCS)2 and Ru2Cu(dpa)4(NCS)2, both of which meet the first criterion for rectification in so much as they are physically asymmetric. In both cases the dominant transport channel is a doubly degenerate [small pi]* orbital localised, to a first approximation, on the Ru2 unit. As a result, current is limited by tunnelling across the Au-SCN-Ni/Cu junction. The paramagnetic Ni centre tunes the left-right delocalisation of the channel, making the minority-spin ([small beta]) channel more transparent than its spin-[small alpha] counterpart and this difference provides the basis for asymmetry in the current under forward and reverse bias.
    Keywords: ATK, Application, transition-metal rectifier
    Area: molecular electronics
    BibTeX:
    @article{Weng2014,
      author = {Weng, Tingting and DeBrincat, Daniel and Arcisauskaite, Vaida and McGrady, John E.},
      title = {In search of structure-function relationships in transition-metal based rectifiers},
      journal = {Inorg. Chem. Front.},
      publisher = {The Royal Society of Chemistry},
      year = {2014},
      volume = {1},
      pages = {468-477},
      doi = {http://dx.doi.org/10.1039/C4QI00038B}
    }
    
    Qiu-Hua Wu, Peng Zhao & De-Sheng Liu A First-principles Study of Spin-polarized Transport Properties of a Co-coordination Complex 2014 Chinese Phys. Lett.
    Vol. 31(6), 067302 
    DOI  
    Abstract: Based on non-equilibrium Green's function formalism and density functional theory calculations, we investigate the spin-polarized transport properties of a Co-coordination complex between two gold electrodes, in which a Co ion is trapped between two 4-mercaptopyridine molecules. Our results demonstrate that the transmission spectra of the system show distinctive features in the spin-up and spin-down channels. Moreover, the current-voltage curves confirm that the system can exhibit robust spin-filtering effect at finite bias voltage, giving the system potential in molecular spintronics applications.
    Keywords: ATK, Application, gold electrode, spintronics
    Area: molecular electronics, spin
    BibTeX:
    @article{Wu2014c,
      author = {Wu, Qiu-Hua and Zhao, Peng and Liu, De-Sheng},
      title = {A First-principles Study of Spin-polarized Transport Properties of a Co-coordination Complex},
      journal = {Chinese Phys. Lett.},
      publisher = {IOP Publishing},
      year = {2014},
      volume = {31},
      number = {6},
      pages = {067302},
      doi = {http://dx.doi.org/10.1088/0256-307x/31/6/067302}
    }
    
    Serhan Yamacli Voltage-dependent parameter extraction for graphene nanoribbon interconnect model through ab initio approach 2014 Thin Solid Films
    Vol. 562, 538 - 542 
    DOI  
    Abstract: This paper presents electrical parameter extraction for metallic graphene nanoribbon (GNR) interconnects utilizing ab initio approach. Unlike the studies taking the kinetic inductance, quantum capacitance and Fermi velocity as constant values, voltage-dependencies of these parameters are obtained for GNR transmission line model. The variations of the kinetic energy and the current by the applied voltage are taken as bases for voltage-dependent kinetic inductance calculation. Quantum capacitance and the Fermi velocity are also computed from the kinetic inductance variation. It is concluded that voltage-dependencies of the kinetic inductance and the quantum capacitance have to be taken into account for accurate GNR modelling in nanoelectronic design.
    Keywords: Kinetic inductance, Quantum capacitance, Fermi velocity, Graphene nanoribbons, Interconnects, Ab initio, ATK, Application
    Area: graphene
    BibTeX:
    @article{Yamacli2014a,
      author = {Serhan Yamacli},
      title = {Voltage-dependent parameter extraction for graphene nanoribbon interconnect model through ab initio approach },
      journal = {Thin Solid Films},
      year = {2014},
      volume = {562},
      pages = {538 - 542},
      doi = {http://dx.doi.org/10.1016/j.tsf.2014.04.095}
    }
    
    Yan-Hong Zhou, Jing Zeng & Ke-Qiu Chen Spin filtering effect and magnetoresistance in zigzag 6, 6, 12-graphyne nanoribbon system 2014 Carbon
    Vol. 76, 175 - 182 
    DOI  
    Abstract: The electronic transport properties of zigzag 6, 6, 12-graphyne nanoribbons (6, 6, 12-Z GYNRs) are investigated by first-principles calculations. The results show that the two bands around the Fermi level of 4-6, 6, 12-ZGYNR are not flat but cambered, which is different from that of zigzag graphene and α-graphyne nanoribbons, and is also different from that of 5-6, 6, 12-ZGYNR. In non-magnetic states, the current across the 5-6, 6, 12-ZGYNR system is almost forbidden even at rather large bias voltages, while in 4-6, 6, 12-ZGYNR system, the current increases linearly with the increase of bias voltage. In spin-polarized state, fine spin filtering effect is gained in anti-parallel configuration of 5-6, 6, 12-ZGYNR system. Moreover, it is found that magnetoresistance exists in the 5-6, 6, 12-ZGYNR system, but not in the 4-6, 6, 12-ZGYNR system.
    Keywords: ATK, Application, spin filtering, magnetoresistance, graphyne
    Area: graphene, spin
    BibTeX:
    @article{Zhou2014a,
      author = {Yan-Hong Zhou and Jing Zeng and Ke-Qiu Chen},
      title = {Spin filtering effect and magnetoresistance in zigzag 6, 6, 12-graphyne nanoribbon system },
      journal = {Carbon},
      year = {2014},
      volume = {76},
      pages = {175 - 182},
      doi = {http://dx.doi.org/10.1016/j.carbon.2014.04.065}
    }
    
    Fengxia Zu, Zuli Liu, Kailun Yao, Guoying Gao, Huahua Fu, Sicong Zhu, Yun Ni & Li Peng Nearly Perfect Spin Filter, Spin Valve and Negative Differential Resistance Effects in a Fe4-based Single-molecule Junction 2014 Scientific Reports
    Vol. 4, 4838 
    DOI  
    Abstract: The spin-polarized transport in a single-molecule magnet Fe4 sandwiched between two gold electrodes is studied, using nonequilibrium Green's functions in combination with the density-functional theory. We predict that the device possesses spin filter effect (SFE), spin valve effect (SVE), and negative differential resistance (NDR) behavior. Moreover, we also find that the appropriate chemical ligand, coupling the single molecule to leads, is a key factor for manipulating spin-dependent transport. The device containing the methyl ligand behaves as a nearly perfect spin filter with efficiency approaching 100%, and the transport is dominated by transmission through the Fe4 metal center. However, in the case of phenyl ligand, the spin filter effect seems to be reduced, but the spin valve effect is significantly enhanced with a large magnetoresistance ratio, reaching 1800%. This may be attributed to the blocking effect of the phenyl ligands in mediating transport. Our findings suggest that such a multifunctional molecular device, possessing SVE, NDR and high SFE simultaneously, would be an excellent candidate for spintronics of molecular devices.
    Keywords: ATK, Application, spin filter, spin valve, negative differential resistance, single-molecule junction
    Area: molecular electronics, spin
    BibTeX:
    @article{Zu2014,
      author = {Zu, Fengxia and Liu, Zuli and Yao, Kailun and Gao, Guoying and Fu, Huahua and Zhu, Sicong and Ni, Yun and Peng, Li},
      title = {Nearly Perfect Spin Filter, Spin Valve and Negative Differential Resistance Effects in a Fe4-based Single-molecule Junction},
      journal = {Scientific Reports},
      publisher = {Nature Publishing Group},
      year = {2014},
      volume = {4},
      pages = {4838},
      doi = {http://dx.doi.org/10.1038/srep04838}
    }
    
    Towfiq Ahmed, Jason T Haraldsen, John J Rehr, Massimiliano Di Ventra, Ivan Schuller & Alexander V Balatsky Correlation dynamics and enhanced signals for the identification of serial biomolecules and DNA bases 2014 Nanotechnology
    Vol. 25(12), 125705 
    DOI  
    Abstract: Nanopore-based sequencing has demonstrated a significant potential for the development of fast, accurate, and cost-efficient fingerprinting techniques for next generation molecular detection and sequencing. We propose a specific multilayered graphene-based nanopore device architecture for the recognition of single biomolecules. Molecular detection and analysis can be accomplished through the detection of transverse currents as the molecule or DNA base translocates through the nanopore. To increase the overall signal-to-noise ratio and the accuracy, we implement a new 'multi-point cross-correlation' technique for identification of DNA bases or other molecules on the single molecular level. We demonstrate that the cross-correlations between each nanopore will greatly enhance the transverse current signal for each molecule. We implement first-principles transport calculations for DNA bases surveyed across a multilayered graphene nanopore system to illustrate the advantages of the proposed geometry. A time-series analysis of the cross-correlation functions illustrates the potential of this method for enhancing the signal-to-noise ratio. This work constitutes a significant step forward in facilitating fingerprinting of single biomolecules using solid state technology.
    Keywords: ATK, Application, graphene, nanoribbon
    Area: graphene
    BibTeX:
    @article{Ahmed2014,
      author = {Towfiq Ahmed and Jason T Haraldsen and John J Rehr and Massimiliano Di Ventra and Ivan Schuller and Alexander V Balatsky},
      title = {Correlation dynamics and enhanced signals for the identification of serial biomolecules and DNA bases},
      journal = {Nanotechnology},
      year = {2014},
      volume = {25},
      number = {12},
      pages = {125705},
      doi = {http://dx.doi.org/10.1088/0957-4484/25/12/125705}
    }
    
    Feras Al-Dirini, Faruque M. Hossain, Ampalavanapillai Nirmalathas & Efstratios Skafidas All-Graphene Planar Self-Switching MISFEDs, Metal-Insulator-Semiconductor Field-Effect Diodes 2014 Scientific Reports
    Vol. 4, 3983 
    DOI  
    Abstract: Graphene normally behaves as a semimetal because it lacks a bandgap, but when it is patterned into nanoribbons a bandgap can be introduced. By varying the width of these nanoribbons this band gap can be tuned from semiconducting to metallic. This property allows metallic and semiconducting regions within a single Graphene monolayer, which can be used in realising two-dimensional (2D) planar Metal-Insulator-Semiconductor field effect devices. Based on this concept, we present a new class of nano-scale planar devices named Graphene Self-Switching MISFEDs (Metal-Insulator-Semiconductor Field-Effect Diodes), in which Graphene is used as the metal and the semiconductor concurrently. The presented devices exhibit excellent current-voltage characteristics while occupying an ultra-small area with sub-10 nm dimensions and an ultimate thinness of a single atom. Quantum mechanical simulation results, based on the Extended Huckel method and Nonequilibrium Green's Function Formalism, show that a Graphene Self-Switching MISFED with a channel as short as 5 nm can achieve forward-to-reverse current rectification ratios exceeding 5000.
    Keywords: electronic and spintronic devices, electrical and electronic engineering, electronic properties and devices, ATK, application, nanoribbon, graphene
    Area: graphene
    BibTeX:
    @article{Al-Dirini2014b,
      author = {Al-Dirini, Feras and Hossain, Faruque M. and Nirmalathas, Ampalavanapillai and Skafidas, Efstratios},
      title = {All-Graphene Planar Self-Switching MISFEDs, Metal-Insulator-Semiconductor Field-Effect Diodes},
      journal = {Scientific Reports},
      publisher = {Nature Publishing Group},
      year = {2014},
      volume = {4},
      pages = {3983},
      doi = {http://dx.doi.org/10.1038/srep03983}
    }
    
    Masaaki Araidai, Takahiro Yamamoto & Kenji Shiraishi Asymmetric behavior of current-induced magnetization switching in a magnetic tunnel junction: Non-equilibrium first-principles calculations 2014 Applied Physics Express
    Vol. 7(4), 045202 
    DOI  
    Abstract: We investigated the microscopic mechanisms of current-induced magnetization switching (CIMS) in an Fe/MgO(001)/Fe/Ta magnetic tunnel junction using non-equilibrium first-principles calculations. We found that the change in the magnetization configuration from antiparallel (AP) to parallel (P) can be realized with a lower electrical power than that from P to AP. From detailed analyses of the density of states subject to a finite bias voltage, we clarified that the asymmetric behavior originates from the difference in the electron scattering processes between switching directions.
    Keywords: ATK, Application, graphene, Fe-MgO-Fe-Ta, MTJ, magnetic tunnel junction
    Area: spintronics
    BibTeX:
    @article{Araidai2014,
      author = {Masaaki Araidai and Takahiro Yamamoto and Kenji Shiraishi},
      title = {Asymmetric behavior of current-induced magnetization switching in a magnetic tunnel junction: Non-equilibrium first-principles calculations},
      journal = {Applied Physics Express},
      year = {2014},
      volume = {7},
      number = {4},
      pages = {045202},
      doi = {http://dx.doi.org/10.7567/APEX.7.045202}
    }
    
    S Barzilai, F Tavazza & L E Levine Effect of wire configuration and point defects on the conductance of gold nano-conductors 2014 Modelling and Simulation in Materials Science and Engineering
    Vol. 22(3), 035006 
    DOI  
    Abstract: Gold nanowire (NW) chains are considered a good candidate for nano-electronics devices because they exhibit remarkable structural and electrical properties. One promising nano-conductor candidate is called 'Hexa1'. It has a two-dimensional, one atom thick structure and was found to spontaneously form during simulations of gold NWs elongations. It is stable and a good conductor when adsorbed on a suitable substrate. In this study, we deepened the investigation of such a NW structure, to explore the effect of the NWs length, point defects and NW junctions on its conductance. We found that the conductance is not affected by the NW length, and that conveniently placed point defects can be used to create resistors. We also found that direction changes in circuits produce conductance bottle necks, therefore decreasing the conductance. However, this decrease can be easily overcome by adding a few atoms to the NW junction.
    Keywords: conductance, gold nanowire, ab initio calculations, ATK, Application, junction
    Area: nanowires
    BibTeX:
    @article{Barzilai2014,
      author = {S Barzilai and F Tavazza and L E Levine},
      title = {Effect of wire configuration and point defects on the conductance of gold nano-conductors},
      journal = {Modelling and Simulation in Materials Science and Engineering},
      year = {2014},
      volume = {22},
      number = {3},
      pages = {035006},
      doi = {http://dx.doi.org/10.1088/0965-0393/22/3/035006}
    }
    
    Tong Chen, Xiaofei Li, Lingling Wang, Kaiwu Luo, Quan Li, Xianghua Zhang & Xiongjun Shang Perfect spin filter and strong current polarization in carbon atomic chain with asymmetrical connecting points 2014 Europhysics Letters
    Vol. 105(5), 57003 
    DOI  
    Abstract: The spin-dependent electron transport properties through a single-carbon atomic chain (SCAC) sandwiched between two-zigzag-graphene-nanoribbon (zGNR) electrodes are investigated by performing first-principles calculations based on the nonequilibrium Green's function (NEGF) approach in combination with spin density functional theory (DFT). Our calculations show that SCAC connecting two zGNRs with asymmetry-contacting points is a perfect spin filter in the transmission function within a large energy range. Moreover, the spin-dependent electron transmission spectra exhibit robust transport polarization characteristics and a strong current polarization behavior (almost 100%) can be found. The microscopic mechanisms are proposed for the spin-related phenomena.
    Keywords: ATK, Application, spin filter, carbon atomic chain, graphene nanoribbon
    Area: graphene, spintronics
    BibTeX:
    @article{Chen2014b,
      author = {Tong Chen and Xiaofei Li and Lingling Wang and Kaiwu Luo and Quan Li and Xianghua Zhang and Xiongjun Shang},
      title = {Perfect spin filter and strong current polarization in carbon atomic chain with asymmetrical connecting points},
      journal = {Europhysics Letters},
      year = {2014},
      volume = {105},
      number = {5},
      pages = {57003},
      doi = {http://dx.doi.org/10.1209/0295-5075/105/57003}
    }
    
    Naoki Harada, Shintaro Sato & Naoki Yokoyama Computational study on electrical properties of transition metal dichalcogenide field-effect transistors with strained channel 2014 Journal of Applied Physics
    Vol. 115(3), 034505 
    DOI  
    Abstract: The performance limits of monolayer transition metal dichalcogenide (TMDC) field-effect transistors (FETs) with isotropic biaxial strain were examined with the "top-of-the-barrier" ballistic MOSFET model. Using a first-principle theory, we calculated the band structures and density of states of strained monolayer MoS2 and WS2, and used the results in model calculations. Introducing strain moves the positions of the conduction band minimum and valence band maximum in k-space with resultant variation in the effective mass and population of carriers. Introducing 2% tensile strain into n-type MoS2 FETs decreases the electron effective mass and, at the same time, increases energy separation between the lower and the higher valleys in the conduction band, resulting in 26% improvement of the ON current up to 1260 A/m. Whereas compressive strain results in complicated effects, -2% strain also improves the ON current by 15%. These results suggest that introducing artificial strain is promising to improve TMDC FET performance.
    Keywords: ATK, Application, transition metal dichalcogenide, FET, field effeect transistor, MoS2, WS2,
    Area: graphene
    BibTeX:
    @article{Harada2014,
      author = {Naoki Harada and Shintaro Sato and Naoki Yokoyama},
      title = {Computational study on electrical properties of transition metal dichalcogenide field-effect transistors with strained channel},
      journal = {Journal of Applied Physics},
      year = {2014},
      volume = {115},
      number = {3},
      pages = {034505},
      doi = {http://dx.doi.org/10.1063/1.4861726}
    }
    
    Yuanyuan He, Jinjiang Zhang & Jianwei Zhao Theoretical Investigation on the Electronic Transport Properties of Iron(II) Porphyrin for CO Sensing with Single-walled Carbon Nanotubes 2014 Chemistry Letters
    Vol. 43(5), 735-737 
    DOI  
    Abstract: We studied the electronic transport properties of a new type of iron(II) porphyrin (PP-Fe) chemosensor for CO with two single-walled carbon nanotube (SWCNT) electrodes, using the first-principle density functional theory. Owing to the fact that electron does not pass through the Fe center when the CO molecule is absorbed to PP-Fe, leading to a considerable difference between the I-V curves of PP-Fe before and after CO absorption, it has great potential for application as a chemical sensor for CO.
    Keywords: ATK, Application, carbon nanotubes, sensor
    Area: nanotubes
    BibTeX:
    @article{He2014a,
      author = {Yuanyuan He and Jinjiang Zhang and Jianwei Zhao},
      title = {Theoretical Investigation on the Electronic Transport Properties of Iron(II) Porphyrin for CO Sensing with Single-walled Carbon Nanotubes},
      journal = {Chemistry Letters},
      year = {2014},
      volume = {43},
      number = {5},
      pages = {735-737},
      doi = {http://dx.doi.org/10.1246/cl.140016}
    }
    
    Ganesh Hegde & R. Chris Bowen Effect of realistic metal electronic structure on the lower limit of contact resistivity of epitaxial metal-semiconductor contacts 2014 Applied Physics Letters
    Vol. 105(5), 053511 
    DOI  
    Abstract: The effect of realistic metal electronic structure on the lower limit of resistivity in [100] oriented n-Si is investigated using full band Density Functional Theory and Semi-Empirical Tight Binding calculations. It is shown that the "ideal metal" assumption may fail in some situations and, consequently, underestimate the lower limit of contact resistivity in n-Si by at least an order of magnitude at high doping concentrations. The mismatch in transverse momentum space in the metal and the semiconductor, the so-called "valley filtering effect," is shown to be sensitive to the details of the transverse boundary conditions for the unit cells used. The results emphasize the need for explicit inclusion of the metal atomic and electronic structure in the atomistic modeling of transport across metal-semiconductor contacts.
    Keywords: sensor, contact resistance, metal-semiconductor contact, ATK, Application
    Area: semi, interfaces
    BibTeX:
    @article{Hegde2014,
      author = {Hegde, Ganesh and Chris Bowen, R.},
      title = {Effect of realistic metal electronic structure on the lower limit of contact resistivity of epitaxial metal-semiconductor contacts},
      journal = {Applied Physics Letters},
      year = {2014},
      volume = {105},
      number = {5},
      pages = {053511},
      doi = {http://dx.doi.org/10.1063/1.4892559}
    }
    
    Guomin Ji, Bin Cui, Yuqing Xu, Changfeng Fang, Wenkai Zhao, Dongmei Li & Desheng Liu Enhanced rectifying performance by asymmetrical gate voltage for BDC20 molecular devices 2014 RSC Advances
    Vol. 4, 16537-16544 
    DOI  
    Abstract: By applying the asymmetrical gate voltage on the 1,4-bis (fullero[c]pyrrolidin-1-yl) benzene BDC20 molecule, we investigate theoretically its electronic transport properties using the density functional theory and nonequilibrium Green's function formalism for a unimolecule device with metal electrodes. Interestingly, the rectifying characteristic with very high rectification ratio, 91.7 and 24.0, can be obtained when the gate voltage is asymmetrically applied on the BDC20 molecular device. The rectification direction can be tuned by the different gate voltage applying regions. The rectification behavior is understood in terms of the evolution of the transmission spectrum and projected density of states spectrum with applied bias combined with molecular projected self-consistent Hamiltonian states analyses. Our finding implies that to realize and greatly promote rectifying performance of the BDC20 molecule the variable gate voltage applying position might be a key issue.
    Keywords: ATK, Application, molecular electronics, rectification
    Area: molecular electronics
    BibTeX:
    @article{Ji2014,
      author = {Ji, Guomin and Cui, Bin and Xu, Yuqing and Fang, Changfeng and Zhao, Wenkai and Li, Dongmei and Liu, Desheng},
      title = {Enhanced rectifying performance by asymmetrical gate voltage for BDC20 molecular devices},
      journal = {RSC Advances},
      publisher = {The Royal Society of Chemistry},
      year = {2014},
      volume = {4},
      pages = {16537-16544},
      doi = {http://dx.doi.org/10.1039/C3RA47408A}
    }
    
    Jian-Chang Li, Jun-Zhi Wu, Xing Gong & Cheng Zhou Electron transport of oligothiophene derivative molecular device at varied temperature and light illumination 2014 Organic Electronics
    Vol. 15(5), 1018 - 1027 
    DOI  
    Abstract: The charge transport of thiol-functionalized thiophene molecular wire incorporated with an alfa-hydroxyphenyl pyridine group was investigated by a soft stamp-printing approach. Current-voltage characteristics were measured from 95 up to 299 K under both dark and light conditions. The molecular junction exhibits asymmetric conducting characteristics and reversible optoelectronic switching; the on/off ratio at 95 K is of 3 orders of magnitude. The experimental data was analyzed using the Simmons and Fowler-Nordheim tunneling models. The effective barrier height of device is greatly affected by substrate temperature, light illumination and bias polarity. The degree of electronic coupling between the top electrode and molecule has a great impact on the junction charge transport. Reproducible negative differential resistance was also observed at low temperature in dark. The first-principle calculations show that the conduction mainly takes place through the lowest unoccupied molecular orbital of the molecular wire, and the negative differential resistance may result from effect of resonant tunneling.
    Keywords: Charge transport, Metal-molecule-metal junction, Self-assembled monolayers, Optoelectronic switching, Negative differential resistance, ATK, Application
    Area: molecular electronics
    BibTeX:
    @article{Li2014b,
      author = {Jian-Chang Li and Jun-Zhi Wu and Xing Gong and Cheng Zhou},
      title = {Electron transport of oligothiophene derivative molecular device at varied temperature and light illumination},
      journal = {Organic Electronics},
      year = {2014},
      volume = {15},
      number = {5},
      pages = {1018 - 1027},
      doi = {http://dx.doi.org/10.1016/j.orgel.2014.02.012}
    }
    
    Xin-Mei Li, Meng-Qiu Long, Li-Ling Cui, Jin Xiao & Hui Xu Electronic and transport properties of V-shaped defect zigzag MoS2 nanoribbons 2014 Chinese Phys. B
    Vol. 23(4), 047307 
    DOI  
    Abstract: Based on the nonequilibrium Green's function (NEGF) in combination with density functional theory (DFT) calculations, we study the electronic structures and transport properties of zigzag MoS2 nanoribbons (ZMNRs) with V-shaped vacancy defects on the edge. The vacancy formation energy results show that the zigzag vacancy is easier to create on the edge of ZMNR than the armchair vacancy. Both of the defects can make the electronic band structures of ZMNRs change from metal to semiconductor. The calculations of electronic transport properties depict that the currents drop off clearly and rectification ratios increase in the defected systems. These effects would open up possibilities for their applications in novel nanoelectronic devices.
    Keywords: electron transport, zigzag MoS2 nanoribbons, V-shaped defect, first-principles, ATK, Application
    Area: graphene
    BibTeX:
    @article{Li2014d,
      author = {Li, Xin-Mei and Long, Meng-Qiu and Cui, Li-Ling and Xiao, Jin and Xu, Hui},
      title = {Electronic and transport properties of V-shaped defect zigzag MoS2 nanoribbons},
      journal = {Chinese Phys. B},
      publisher = {IOP Publishing},
      year = {2014},
      volume = {23},
      number = {4},
      pages = {047307},
      doi = {http://dx.doi.org/10.1088/1674-1056/23/4/047307}
    }
    
    K.M. Liew, Ming Qiu & Chris Yuan First-principles study of rectifying and switching behavior for different contact positions between sulfur-terminated armchair graphene nanoribbons junctions 2014 Europhysics Letters
    Vol. 105(5), 58005 
    DOI  
    Abstract: Transport properties of armchair graphene nanoribbon junctions with different widths are investigated on the zigzag edges terminated with sulfur atoms. The first-principles calculations based on the non-equilibrium Green's functions together with the density-functional theory show that their I-V characteristics display obvious rectifying performance and switching behavior which are sensitive to the contact points and external activation. The analysis of the Mulliken charge distribution and projected Hamiltonian energy spectrum provides an inside view of the electronic structure of the ground state. The non-equilibrium states analysis, incorporating the density of states and projected density of states as well as the evolutions of frontier orbitals under various external biases, reveals that the intrinsic origin of the different rectifying performances is a result of the asymmetric movement of conducting states and contributing orbitals.
    Keywords: Molecular electronic devices, Electronic transport in graphene, Electronic transport in mesoscopic systems, ATK, Application
    Area: graphene
    BibTeX:
    @article{Liew2014,
      author = {K. M. Liew and Ming Qiu and Chris Yuan},
      title = {First-principles study of rectifying and switching behavior for different contact positions between sulfur-terminated armchair graphene nanoribbons junctions},
      journal = {Europhysics Letters},
      year = {2014},
      volume = {105},
      number = {5},
      pages = {58005},
      doi = {http://dx.doi.org/10.1209/0295-5075/105/58005}
    }
    
    A. Mahmoud & P. Lugli Toward Circuit Modeling of Molecular Devices 2014 IEEE Transactions on Nanotechnology
    Vol. 13(3), 510-516 
    DOI  
    Abstract: Modeling and simulation tools play a crucial role in the rapid development of semiconductor technologies as they reduce the required prototype mycles and costs. Molecular electronic is one of the promising technologies that are currently gaining a lot of interest in the research community. Usually, theoretical studies in the field of molecular electronics have been concerned with the understanding and explanation of the physics behind the quantum phenomena observed at this very small scale. Despite the existence of outstanding publications for modeling molecular devices, none of them targets the circuit modeling of molecules. As happened for semiconductors, the availability of solid-circuit modeling can open the way to molecular systems design tools and, therefore, to application. In this paper, we present a first attempt to model molecular devices with circuit elements. The model is applied to various available molecular devices, and the results have been validated versus available experimental and first-principles results. The circuit modeling is further verified by atomistic simulation of the testbed molecules.
    Keywords: circuit simulation;molecular electronics;atomistic simulation;circuit elements;circuit simulation tools;molecular devices;molecular electronic;molecular system design tools;quantum phenomena;semiconductor technology;solid-circuit modeling;Couplings;Electric potential;Electrodes;Integrated circuit modeling;Logic gates;Solid modeling;Transistors;Circuit modeling;molecular devices;nonequilibrium Green's Function (NEGF), ATK, Application
    Area: molecular electronics
    BibTeX:
    @article{Mahmoud2014a,
      author = {Mahmoud, A. and Lugli, P.},
      title = {Toward Circuit Modeling of Molecular Devices},
      journal = {IEEE Transactions on Nanotechnology},
      year = {2014},
      volume = {13},
      number = {3},
      pages = {510-516},
      doi = {http://dx.doi.org/10.1109/TNANO.2014.2308257}
    }
    
    Y. Min, J.H. Fang, C.G. Zhong, Z.C. Dong, C.N. Wang, T.L. Xue & K.L. Yao Contact transparency inducing negative differential resistance in nanotube-molecule-nanotube junction predicted by first-principles study 2014 Physics Letters A
    Vol. 378(16-17), 1170 - 1173 
    DOI  
    Abstract: We construct a molecular junction where propyl contacts two armchair carbon nanotubes through five-member ring and perform the first-principles calculations of its transport properties. The negative differential resistance effect with peak-to-valley ratio of 700% is present. Our investigations indicate that contact transparency can induce negative differential resistance in nanotube-molecule-nanotube junction, which may promise the potential application in nano-electronics devices in the future.
    Keywords: First-principles, Carbon nanotube, Molecular electronics, Nano-electronics, Negative differential resistance, ATK, Application
    Area: molecular electronics
    BibTeX:
    @article{Min2014a,
      author = {Y. Min and J.H. Fang and C.G. Zhong and Z.C. Dong and C.N. Wang and T.L. Xue and K.L. Yao},
      title = {Contact transparency inducing negative differential resistance in nanotube-molecule-nanotube junction predicted by first-principles study},
      journal = {Physics Letters A },
      year = {2014},
      volume = {378},
      number = {16-17},
      pages = {1170 - 1173},
      doi = {http://dx.doi.org/10.1016/j.physleta.2014.02.021}
    }
    
    Yun Ni, Kai-Lun Yao, Chao-Qun Tang, Guo-Ying Gao, Hua-Hua Fu & Si-Cong Zhu Perfect spin-filter, spin-valve, switching and negative differential resistance in an organic molecular device with graphene leads 2014 RSC Advances
    Vol. 4, 18522-18528 
    DOI  
    Abstract: By performing first-principle quantum transport calculations, we proposed a multiple-effect organic molecular device for spintronics. The device is constructed of a perylene tetracarboxylic diimide molecule sandwiched between graphene electrodes. Our calculations show that the device has several perfect spintronics effects such as a spin-filter effect, a magnetoresistance effect, a negative differential resistance effect and a spin switching effect. These results indicate that our one-dimensional molecular device is a promising candidate for the future application of graphene-based organic spintronics devices.
    Keywords: ATK, Application, spin filter, spin valve, switching, dirrerential resistance, graphene
    Area: spintronics
    BibTeX:
    @article{Ni2014,
      author = {Ni, Yun And Yao, Kai-Lun and Tang, Chao-Qun and Gao, Guo-Ying and Fu, Hua-Hua and Zhu, Si-Cong},
      title = {Perfect spin-filter, spin-valve, switching and negative differential resistance in an organic molecular device with graphene leads},
      journal = {RSC Advances},
      publisher = {The Royal Society of Chemistry},
      year = {2014},
      volume = {4},
      pages = {18522-18528},
      doi = {http://dx.doi.org/10.1039/C3RA48069K}
    }
    
    Sumeet C. Pandey, Roy Meade & Gurtej S. Sandhu Cu impurity in insulators and in metal-insulator-metal structures: Implications for resistance-switching random access memories 2015 Journal of Applied Physics
    Vol. 117(5), 054504 
    DOI  
    Abstract: We present numerical results from atomistic simulations of Cu in SiO2 and Al2O3, with an emphasis on the thermodynamic, kinetic, and electronic properties. The calculated properties of Cu impurity at various concentrations (9.91E+20 cm-3 and 3.41E+22 cm-3) in bulk oxides are presented. The metal-insulator interfaces result in up to a 4 eV reduction in the formation energies relative to the crystalline bulk. Additionally, the importance of Cu-Cu interaction in lowering the chemical potential is introduced. These concepts are then discussed in the context of formation and stability of localized conductive paths in resistance-switching Random Access Memories (RRAM-M). The electronic density of states and non-equilibrium transmission through these localized paths are studied, confirming conduction by showing three orders of magnitude increase in the electron transmission. The dynamic behavior of the conductive paths is investigated with atomistic drift-diffusion calculations. Finally, the paper concludes with a molecular dynamics simulation of a RRAM-M cell that attempts to combine the aforementioned phenomena in one self-consistent model.
    Keywords: ATK, Application, metal-insulator interface, switching
    Area: semi, interfaces, nvm
    BibTeX:
    @article{Pandey2015,
      author = {Pandey, Sumeet C. and Meade, Roy and Sandhu, Gurtej S.},
      title = {Cu impurity in insulators and in metal-insulator-metal structures: Implications for resistance-switching random access memories},
      journal = {Journal of Applied Physics},
      year = {2015},
      volume = {117},
      number = {5},
      pages = {054504},
      doi = {http://dx.doi.org/10.1063/1.4907578}
    }
    
    Li Shao, Guangde Chen, Honggang Ye, Haibo Niu, Yelong Wu, Youzhang Zhu & Bingjun Ding Sulfur dioxide molecule sensors based on zigzag graphene nanoribbons with and without Cr dopant 2014 Physics Letters A
    Vol. 378(7-8), 667 - 671 
    DOI  
    Abstract: Structure, electronic, and transport properties of sulfur dioxide (SO2) molecule adsorbed on pure and Cr doped zigzag graphene nanoribbons (ZGNRs) are investigated by means of first principle density functional theory and nonequilibrium Green's function computations. It is found that Cr doped ZGNR is more sensitive to SO2 molecule than pure ZGNR. The pure ZGNRs with and without SO2 molecule show similar I-V curves, but the current of Cr doped ZGNR will significant increase after SO2 molecule adsorption.
    Keywords: Graphene nanoribbon, SO2, Molecule sensor, First principle, ATK, Application
    Area: graphene
    BibTeX:
    @article{Shao2014,
      author = {Li Shao and Guangde Chen and Honggang Ye and Haibo Niu and Yelong Wu and Youzhang Zhu and Bingjun Ding},
      title = {Sulfur dioxide molecule sensors based on zigzag graphene nanoribbons with and without Cr dopant},
      journal = {Physics Letters A},
      year = {2014},
      volume = {378},
      number = {7-8},
      pages = {667 - 671},
      doi = {http://dx.doi.org/10.1016/j.physleta.2013.12.042}
    }
    
    Caihua Shen, Juan Liu, N. Jiao, C.X. Zhang, Huaping Xiao, R.Z. Wang & L.Z. Sun Transport properties of graphene/metal planar junction 2014 Physics Letters A
    Vol. 378(18-19), 1321 - 1325 
    DOI  
    Abstract: The transport properties of graphene/metal (Cu(111), Al(111), Ag(111), and Au(111)) planar junction are investigated using the first-principles nonequilibrium Green's function method. The planar junction induce second transmission minimum (TM2) below the Fermi level due to the existence of the Dirac point of clamped graphene. Interestingly, no matter the graphene is p- or n-type doped by the metal substrate, the TM2 always locates below the Fermi level. We find that the position of the TM2 is not only determined by the doping effect of metal lead on the graphene, but also influenced by the electrostatic potential of the metal substrate and the work function difference between the clamped and suspended graphene.
    Keywords: Graphene/metal planar junction, First-principles calculation, Transmission minimum, Work function difference, Electrostatic potential, ATK, Application
    Area: graphene
    BibTeX:
    @article{Shen2014,
      author = {Caihua Shen and Juan Liu and N. Jiao and C.X. Zhang and Huaping Xiao and R.Z. Wang and L.Z. Sun},
      title = {Transport properties of graphene/metal planar junction},
      journal = {Physics Letters A},
      year = {2014},
      volume = {378},
      number = {18-19},
      pages = {1321 - 1325},
      doi = {http://dx.doi.org/10.1016/j.physleta.2014.03.008}
    }
    
    Anurag Srivastava, Sumit Kumar Jain & Purnima Swarup Khare Ab-initio study of structural, electronic, and transport properties of zigzag GaP nanotubes 2014 Journal of Molecular Modeling
    Vol. 20(3), 2171 
    DOI  
    Abstract: Stability and electronic properties of zigzag (3
    Keywords: Ab-initio; Band structure; Buckling; GaP; I-V curve; Nanotubes; ATK; Application
    Area: nanotubes
    BibTeX:
    @article{Srivastava2014a,
      author = {Srivastava, Anurag and Jain, Sumit Kumar and Khare, Purnima Swarup},
      title = {Ab-initio study of structural, electronic, and transport properties of zigzag GaP nanotubes},
      journal = {Journal of Molecular Modeling},
      publisher = {Springer Berlin Heidelberg},
      year = {2014},
      volume = {20},
      number = {3},
      pages = {2171},
      doi = {http://dx.doi.org/10.1007/s00894-014-2171-2}
    }
    
    Kengo Takashima & Takahiro Yamamoto Conductance fluctuation of edge-disordered graphene nanoribbons: Crossover from diffusive transport to Anderson localization 2014 Applied Physics Letters
    Vol. 104(9), 093105 
    DOI URL 
    Abstract: Conductance fluctuation of edge-disordered graphene nanoribbons (ED-GNRs) is examined using the non-equilibrium Green's function technique combined with the extended Hückel approximation. The mean free path L and the localization length x of the ED-GNRs are determined to classify the quantum transport regimes. In the diffusive regime where the length Lc of the ED-GNRs is much longer than L and much shorter than x, the conductance histogram is given by a Gaussian distribution function with universal conductance fluctuation. In the localization regime where Lc > x, the histogram is no longer the universal Gaussian distribution but a lognormal distribution that characterizes Anderson localization.
    Keywords: ATK, Application, graphene, nanoribbon, conductance fluctuation, diffusive transport, Anderson localization
    Area: graphene
    BibTeX:
    @article{Takashima2014,
      author = {Takashima, Kengo and Yamamoto, Takahiro},
      title = {Conductance fluctuation of edge-disordered graphene nanoribbons: Crossover from diffusive transport to Anderson localization},
      journal = {Applied Physics Letters},
      year = {2014},
      volume = {104},
      number = {9},
      pages = {093105},
      url = {http://scitation.aip.org/content/aip/journal/apl/104/9/10.1063/1.4867473},
      doi = {http://dx.doi.org/10.1063/1.4867473}
    }
    
    Bo Xiao, Tingkun Gu, Tomofumi Tada & Satoshi Watanabe Conduction paths in Cu/amorphous-Ta2O5/Pt atomic switch: First-principles studies 2014 Journal of Applied Physics
    Vol. 115(3), 034503 
    DOI  
    Abstract: We have examined the structure of Cu filaments in Cu/amorphous-Ta2O5 (a-Ta2O5)/Pt atomic switch from first principles. We have found that the Cu single atomic chains are unstable during the molecular dynamics (MD) simulation and thus cannot work as conduction paths. On the other hand, Cu nanowires with various diameters are stable and can form conductive paths. In this case, the Cu-Cu bonding mainly contributes to the conductive, delocalized defect state. These make a sharp contrast with the case of single Cu chains in crystalline Ta2O5, which can be conductive paths through the alternant Cu-Ta bonding structure. A series of MD simulations suggest that even Cu nanowires with a diameter of 0.24nm can work as conduction paths. The calculations of the transport properties of Cu/a-Ta2O5/Pt heterostructures with Cu nanowires between two electrodes further confirm the conductive nature of the Cu nanowires in the a-Ta2O5.
    Keywords: ATK, Application, conductance paths, atomic switching, filament
    Area: nanowires, semi, interfaces, nvm
    BibTeX:
    @article{Xiao2014,
      author = {Xiao, Bo and Gu, Tingkun and Tada, Tomofumi and Watanabe, Satoshi},
      title = {Conduction paths in Cu/amorphous-Ta2O5/Pt atomic switch: First-principles studies},
      journal = {Journal of Applied Physics},
      year = {2014},
      volume = {115},
      number = {3},
      pages = {034503},
      doi = {http://dx.doi.org/10.1063/1.4861724}
    }
    
    Ehsan Zahedi & Abdolhakim Pangh Current-voltage characteristics through dithienylcyclopentene: A NEGF-DFT study 2014 Physica E
    Vol. 61, 1 - 8 
    DOI  
    Abstract: The nonequilibrium Green's function technique combined with density functional theory were used to investigate the transport properties of 1,2-bis(5-methyl-[2,2'-bithiophen]-4-yl)cyclopent-1-ene optical molecular switch. Both of its closed and open forms have two S-linkers and translated into the Gold junction with the (1 1 1) surfaces. I-V characteristics, differential conductance, on-off ratio, electronic transmission coefficients, spatial distribution of molecular projected self-consistent Hamiltonian (MPSH) orbitals and projected of the density of states spectrums corresponding to the closed and open forms have been calculated and analyzed. The influences of the delocalization degree of MPSH states in the bias window and coupling degree between molecule orbitals and electrodes levels, on the electronic transport of two systems were discussed in detail. Meantime, larger current through the closed form and negative differential resistance behavior were observed and considered.
    Keywords: NEGF-DFT, Transmission, PDOS, MPSH, Negative differential resistance, ATK, Application
    Area: molecular electronics
    BibTeX:
    @article{Zahedi2014,
      author = {Ehsan Zahedi and Abdolhakim Pangh},
      title = {Current-voltage characteristics through dithienylcyclopentene: A NEGF-DFT study},
      journal = {Physica E},
      year = {2014},
      volume = {61},
      pages = {1 - 8},
      doi = {http://dx.doi.org/10.1016/j.physe.2014.03.012}
    }
    
    Jinjiang Zhang, Wei Sun, Hongmei Liu, Yuanyuan He & Jianwei Zhao Effects of terminal connection and molecular length on electron transport in linear conjugated molecular wires 2014 Computational Materials Science
    Vol. 87, 100 - 106 
    DOI  
    Abstract: Electron transport through single linear conjugated molecular wires is investigated by using nonequilibrium Green's function method combined with density functional theory. The investigated molecule is sandwiched between two gold electrodes via S-Au bonds via three different kinds of terminal connections. One of the connections shows an obviously higher electrical conductance than the others. Several factors have been analyzed. Among them terminal coupling and destructive quantum interference play the main role. A significant structural feature of well conductive conjugated molecules has been pointed out which may provide a quick prediction before time-consuming calculations. Furthermore, we find that the conductance of all the studied molecular wires drops first and then increases with the molecular length increasing. This unusual phenomenon is investigated from the tunneling barrier, shift of molecular levels and electronic coupling between molecule and electrodes, and is ascribed to the competition between two opposite groups of factors.
    Keywords: Molecular wire, Nonequilibrium Green's function, Density functional theory, Quantum interference, ATK, Application
    Area: nanowires
    BibTeX:
    @article{Zhang2014c,
      author = {Jinjiang Zhang and Wei Sun and Hongmei Liu and Yuanyuan He and Jianwei Zhao},
      title = {Effects of terminal connection and molecular length on electron transport in linear conjugated molecular wires },
      journal = {Computational Materials Science},
      year = {2014},
      volume = {87},
      pages = {100 - 106},
      doi = {http://dx.doi.org/10.1016/j.commatsci.2014.02.009}
    }
    
    Wen-Kai Zhao, Guo-Min Ji & De-Sheng Liu Contact position and width effect of graphene electrode on the electronic transport properties of dehydrobenzoannulenne molecule under bias 2014 Physics Letters A
    Vol. 378(4), 446 - 452 
    DOI  
    Abstract: By applying nonequilibrium Green's function formalism in combination with density functional theory, we have investigated the electronic transport properties of dehydrobenzoannulenne molecule attached to different positions of the zigzag graphene nanoribbons (ZGNRs) electrode. The different contact positions are found to drastically turn the transport properties of these systems. The negative differential resistance (NDR) effect can be found when the ZGNRs electrodes are mirror symmetry under the xz midplane, and the mechanism of NDR has been explained. Moreover, parity limitation tunneling effect can be found in a certain symmetry two-probe system and it can completely destroy electron tunneling process. The present findings might be useful for the application of ZGNRs-based molecular devices.
    Keywords: Electronic transport, Zigzag graphene nanoribbon, Dehydrobenzoannulenne, Density functional theory, Non-equilibrium Green's function, ATK, Application
    Area: graphene
    BibTeX:
    @article{Zhao2014d,
      author = {Wen-Kai Zhao and Guo-Min Ji and De-Sheng Liu},
      title = {Contact position and width effect of graphene electrode on the electronic transport properties of dehydrobenzoannulenne molecule under bias},
      journal = {Physics Letters A},
      year = {2014},
      volume = {378},
      number = {4},
      pages = {446 - 452},
      doi = {http://dx.doi.org/10.1016/j.physleta.2013.12.006}
    }
    
    Feras Al-Dirini, Faruque M. Hossain, Ampalavanapillai Nirmalathas & Efstratios Skafidas Asymmetrically-gated graphene self-switching diodes as negative differential resistance devices 2014 Nanoscale
    Vol. 6, 7628-7634 
    DOI  
    Abstract: We present an asymmetrically-gated Graphene Self-Switching Diode (G-SSD) as a new negative differential resistance (NDR) device, and study its transport properties using nonequilibrium Green's function (NEGF) formalism and the Extended Huckel (EH) method. The device exhibits a new NDR mechanism, in which a very small quantum tunnelling current is used to control a much-larger channel conduction current, resulting in a very pronounced NDR effect. This NDR effect occurs at low bias voltages, below 1 V, and results in a very high current peak in the $mu A$ range and a high peak-to-valley current ratio (PVCR) of 40. The device has an atomically-thin structure with sub-10 nm dimensions, and does not require any doping or external gating. These results suggest that the device has promising potential in applications such as high frequency oscillators, memory devices, and fast switches.
    Keywords: ATK-SE, Application, graphene, diode, differential resistance, NEGF, extended Huckel
    Area: graphene
    BibTeX:
    @article{Al-Dirini2014,
      author = {Al-Dirini, Feras and Hossain, Faruque M. and Nirmalathas, Ampalavanapillai and Skafidas, Efstratios},
      title = {Asymmetrically-gated graphene self-switching diodes as negative differential resistance devices},
      journal = {Nanoscale},
      publisher = {The Royal Society of Chemistry},
      year = {2014},
      volume = {6},
      pages = {7628-7634},
      doi = {http://dx.doi.org/10.1039/C4NR00112E}
    }
    
    Mausumi Chattopadhyaya, Md. Mehboob Alam, Debasis Sarkar & Swapan Chakrabarti Electrically Controlled Eight-Spin-Qubit Entangled-State Generation in a Molecular Break Junction 2014 ChemPhysChem
    Vol. 15(9), 1747 
    DOI  
    Abstract: The generation of spin-based multi-qubit entangled states in the presence of an electric field is one of the most challenging tasks in current quantum-computing research. Such examples are still elusive. By using non-equilibrium Green's function-based quantum-transport calculations in combination with non-collinear spin density functional theory, we report that an eight-spin-qubit entangled state can be generated with the high-spin state of a dinuclear Fe(II) complex when the system is placed in a molecular break junction. The possible gate operation scheme, gating time, and decoherence issues have been carefully addressed. Furthermore, our calculations reveal that the preservation of the high spin state of this complex is possible if the experimentalists keep the electric-field strength below 0.78 $V nm^-1$. In brief, the present study offers a unique way to realize the first example of a multi-qubit entangled state by electrical means only.
    Keywords: ATK, Application, entanglement, NEGF, quantum interference, quantum transport
    Area: molecular electronics, spin
    BibTeX:
    @article{Chattopadhyaya2014a,
      author = {Chattopadhyaya, Mausumi and Alam, Md. Mehboob and Sarkar, Debasis and Chakrabarti, Swapan},
      title = {Electrically Controlled Eight-Spin-Qubit Entangled-State Generation in a Molecular Break Junction},
      journal = {ChemPhysChem},
      publisher = {WILEY-VCH Verlag},
      year = {2014},
      volume = {15},
      number = {9},
      pages = {1747},
      doi = {http://dx.doi.org/10.1002/cphc.201400029}
    }
    
    X.Q. Deng, Z.H. Zhang, G.P. Tang, Z.Q. Fan & C.H. Yang Spin filtering and large magnetoresistance behaviors in carbon chain-zigzag graphene nanoribbon nanojunctions 2014 Physics Letters A
    Vol. 378(21), 1540 - 1547 
    DOI  
    Abstract: Using the non-equilibrium Green's function method combined with the density functional theory, we investigate the electron and spin transport properties of carbon chains covalently connected with zigzag-edged graphene electrodes at finite bias with the parallel (P) and antiparallel (AP) magnetism configurations. When two zigzag-edged graphene electrodes are H2-ZGNR-H structures, spin filtering effect can be realized only with AP magnetism configuration. While one electrode is replaced with the H-ZGNR-H structure, we observe a dual spin filtering effect with above two magnetism configurations. But the spin transport properties of carbon chains can also be affected by the linking way of the carbon chain ends. Deeper analyses show that the spin-related properties are related to the electrodes, magnetism configurations, and the connection structure between electrodes and carbon chains.
    Keywords: ATK, Application, spin filtering, graphene, spintronics, magnetoresistance
    Area: graphene
    BibTeX:
    @article{Deng2014a,
      author = {X.Q. Deng and Z.H. Zhang and G.P. Tang and Z.Q. Fan and C.H. Yang},
      title = {Spin filtering and large magnetoresistance behaviors in carbon chain-zigzag graphene nanoribbon nanojunctions },
      journal = {Physics Letters A},
      year = {2014},
      volume = {378},
      number = {21},
      pages = {1540 - 1547},
      doi = {http://dx.doi.org/10.1016/j.physleta.2014.03.036}
    }
    
    Maharavo Randrianarivony Multilevel B-Spline Repulsive Energy in Nanomodeling of Graphenes 2014 Journal of Surface Engineered Materials and Advanced Technology
    Vol. 04(02), 75-86 
    DOI  
    Abstract: Quantum energies which are used in applications are usually composed of repulsive and attractive terms. The objective of this study is to use an accurate and efficient fitting of the repulsive energy instead of using standard parametrizations. The investigation is based on Density Functional Theory and Tight Binding simulations. Our objective is not only to capture the values of the repulsive terms but also to efficiently reproduce the elastic properties and the forces. The elasticity values determine the rigidity of a material when some traction or load is applied on it. The pairpotential is based on an exponential term corrected by B-spline terms. In order to accelerate the computations, one uses a hierarchical optimization for the B-splines on different levels. Carbon graphenes constitute the configurations used in the simulations. We report on some results to show the efficiency of the B-splines on different levels.
    Keywords: ATK, Application, Repulsive Potential, B-Spline, Force, Elastic Stress, Hierarchy
    Area: graphene
    BibTeX:
    @article{Randrianarivony2014a,
      author = {Randrianarivony, Maharavo},
      title = {Multilevel B-Spline Repulsive Energy in Nanomodeling of Graphenes},
      journal = {Journal of Surface Engineered Materials and Advanced Technology},
      publisher = {Scientific Research Publishing, Inc,},
      year = {2014},
      volume = {04},
      number = {02},
      pages = {75-86},
      doi = {http://dx.doi.org/10.4236/jsemat.2014.42011}
    }
    
    Qiu-Hua Wu, Peng Zhao & De-Sheng Liu Electronic Transport of a Molecular Photoswitch with Graphene Nanoribbon Electrodes 2014 Chinese Physics Letters
    Vol. 31(5), 057304 
    DOI  
    Abstract: Based on non-equilibrium Green's function formalism and density functional theory calculations, we investigate the electronic transport properties of 15,16-dinitrile dihydropyrene/cyclophanediene bridged between two zigzag graphene nanoribbon electrodes. Our results demonstrate that the system can exhibit good switching behavior with the maximum on-off ratio high up to 146 which is improved dramatically compared with the case of gold electrodes. Moreover, an obvious negative differential resistance behavior occurs at 0.3 V, making the system have more potential in near future molecular circuits.
    Keywords: ATK, Application, graphene, nanoribbon, switching
    Area: graphene
    BibTeX:
    @article{Wu2014d,
      author = {Wu, Qiu-Hua and Zhao, Peng and Liu, De-Sheng},
      title = {Electronic Transport of a Molecular Photoswitch with Graphene Nanoribbon Electrodes},
      journal = {Chinese Physics Letters},
      publisher = {IOP Publishing},
      year = {2014},
      volume = {31},
      number = {5},
      pages = {057304},
      doi = {http://dx.doi.org/10.1088/0256-307x/31/5/057304}
    }
    
    Yanning Wu, Kaiyin Zhang, Yinsheng Huang, Shan Wu, Hui Zhu, Ping Cheng & Jun Ni Superlattice structures of silicene-based armchair nanoribbons by density functional theory calculation 2014 The European Physical Journal B
    Vol. 87(4), 94 
    DOI  
    Abstract: Based on the DFT calculations, the various types of ASiSLs, which are the periodically repeated junctions made of ASiNRs with different widths, have been investigated. The band structures of ASiSLs were modulated by the size and strain of superlattices. The length of the narrow and wide nanoribbons plays interesting roles in the modulation of the electronic structures of ASiSLs. It could alter the band structure, and modify the distribution of the localized and dispersive states of superlattices. With the stain increased, the related energy gaps of ASiSLs will change, which are significantly different with that of the constituent nanoribbons.
    Keywords: ATK, Application, silicene, nanoribbon
    Area: graphene
    BibTeX:
    @article{Wu2014g,
      author = {Wu, Yanning and Zhang, Kaiyin and Huang, Yinsheng and Wu, Shan and Zhu, Hui and Cheng, Ping and Ni, Jun},
      title = {Superlattice structures of silicene-based armchair nanoribbons by density functional theory calculation},
      journal = {The European Physical Journal B},
      publisher = {Springer Berlin Heidelberg},
      year = {2014},
      volume = {87},
      number = {4},
      pages = {94},
      doi = {http://dx.doi.org/10.1140/epjb/e2014-41075-8}
    }
    
    X.F. Yang, Y.S. Liu, X. Zhang, L.P. Zhou, X.F. Wang, F. Chi & J.F. Feng Perfect spin filtering and large spin thermoelectric effects in organic transition-metal molecular junctions 2014 Physical Chemistry Chemical Physics
    Vol. 16, 11349-11355 
    DOI  
    Abstract: We present ab initio studies of spin-polarized transport properties and thermospin effects in cyclopentadienyl-iron molecular junctions. It is found that the spin-up transmission coefficient at the Fermi level shows an odd-even oscillating behaviour, while the spin-down transmission coefficient has an exponential decay with the molecule length. The spin polarization at the Fermi level rapidly tends toward a saturation value close to 100% with the molecule length. This is ascribed to the existence of different orbital states for different spin components at the Fermi level. In addition, we find that the spin-up Seebeck coefficient oscillates between positive and negative values, while the spin-down Seebeck coefficient always has a positive value and monotonically increases with the molecule length. Therefore in some cases, the spin Seebeck coefficient is even larger than the corresponding charge Seebeck effect. Finally, we also provide a possibility of utilizing cyclopentadienyl-iron molecular junctions to achieve the pure spin current without an accompanying charge current at about room temperature.
    Keywords: ATK, Application, molecular junction, spin filtering, thermoelectrics
    Area: moleculart electronics, thermo, spin
    BibTeX:
    @article{Yang2014b,
      author = {Yang, X. F. and Liu, Y. S. and Zhang, X. and Zhou, L. P. and Wang, X. F. and Chi, F. and Feng, J. F.},
      title = {Perfect spin filtering and large spin thermoelectric effects in organic transition-metal molecular junctions},
      journal = {Physical Chemistry Chemical Physics},
      publisher = {The Royal Society of Chemistry},
      year = {2014},
      volume = {16},
      pages = {11349-11355},
      doi = {http://dx.doi.org/10.1039/C4CP00390J}
    }
    
    M. Aruna Bharathi, K. Venkateswara Rao & M. Sushama Synthesis, Characterization and Density Functional Study of LiMn1.5Ni0.5O4 Electrode for Lithium ion Battery 2014 Journal of Nano- and Electronic Physics
    Vol. 6(1), 01005 
    URL 
    Abstract: This paper analyses material issues of development of Li-ion batteries to store electrical energy. The performance of the battery is improved by developing the high energy density cathode materials at Nano level. This paper explains the synthesis of most interesting cathode material Lithium Manganese Spinel and its derivatives like transition metal oxide (LiNi0.5Mn1.5O4) using Co-Precipitation chemical method; it is one of the eco-friendly ,effective, economic and easy preparation method. The structural features of LiNi0.5Mn1.5O4 was characterized by XRD - analysis indicated that prepared sample mainly belong to cubic crystal form with Fd3m space group ,with lattice parameter a 8.265 and average crystal size of 31.59 nm and compared the experimental results with computation details from first principle computation methods with Quantum wise Atomistix Tool Kit (ATK),Virtual Nano Lab. First principle computation methods provide important role in emerging and optimizing this electrode material. In this study we present an overview of the computation approach aimed at building LiNi0.5Mn1.5O4 crystal as cathode for Lithium ion battery. We show each significant property can be related to the structural component in the material and can be computed from first principle. By direct comparison with experimental results, we assume to interpret that first principle computation can help to accelerate the design & development of LiNi0.5Mn1.5O4 as cathode material of lithium ion battery for energy storage.
    Keywords: ATK, Application, Co-precipitation, DFT, Li-ion Battery, LiNi0.5Mn1.5O4, XRD, Transmission spectrum, Band structure, Density of states
    Area: materials, battery
    BibTeX:
    @article{Bharathi2014,
      author = {M. Aruna Bharathi and K. Venkateswara Rao and M. Sushama},
      title = {Synthesis, Characterization and Density Functional Study of LiMn1.5Ni0.5O4 Electrode for Lithium ion Battery},
      journal = {Journal of Nano- and Electronic Physics},
      year = {2014},
      volume = {6},
      number = {1},
      pages = {01005},
      url = {http://jnep.sumdu.edu.ua/download/numbers/2014/1/articles/en/jnep_2014_V6_01005.pdf}
    }
    
    An-Bang Chen, Xue-Feng Wang, P. Vasilopoulos, Ming-Xing Zhai & Yu-Shen Liu Spin-dependent ballistic transport properties and electronic structures of pristine and edge-doped zigzag silicene nanoribbons: large magnetoresistance 2014 Physical Chemistry Chemical Physics
    Vol. 16(11), 5113 
    DOI  
    Abstract: The electronic structure and conductance of substitutionally edge-doped zigzag silicene nanoribbons (ZSiNRs) are investigated using the nonequilibrium Green's function method combined with the density functional theory. Two-probe systems of ZSiNRs in both ferromagnetic and antiferromagnetic states are considered. Doping effects of elements from groups III and V, in a parallel or antiparallel magnetic configuration of the two electrodes, are discussed. By switching on and off the external magnetic field, we may convert the metallic ferromagnetic ZSiNRs into insulating antiferromagnetic ZSiNRs. In the ferromagnetic state, even- or odd-width ZSiNRs exhibit a drastically different magnetoresistance. In an odd-width edge-doped ZSiNR a large magnetoresistance occurs compared to that in a pristine ZSiNR. The situation is reversed in even-width ZSiNRs. These phenomena result from the drastic change in the conductance in the antiparallel configuration.
    Keywords: ATK, Application, silicene, nanoribbon, transport, electronic structure, magnetoresistance, spintronics
    Area: graphene, spin
    BibTeX:
    @article{Chen2014,
      author = {Chen, An-Bang and Wang, Xue-Feng and Vasilopoulos, P. and Zhai, Ming-Xing and Liu, Yu-Shen},
      title = {Spin-dependent ballistic transport properties and electronic structures of pristine and edge-doped zigzag silicene nanoribbons: large magnetoresistance},
      journal = {Physical Chemistry Chemical Physics},
      publisher = {Royal Society of Chemistry (RSC)},
      year = {2014},
      volume = {16},
      number = {11},
      pages = {5113},
      doi = {http://dx.doi.org/10.1039/c3cp55447c}
    }
    
    Liling Cui, Bingchu Yang, Xinmei Li, Jun He & Mengqiu Long Electronic transport properties of transition metal (Cu, Fe) phthalocyanines connecting to V-shaped zigzag graphene nanoribbons 2014 International Journal of Modern Physics B
    Vol. 28(08), 1450019 
    DOI  
    Abstract: Using nonequlilibrium Green's functions in combination with the density-functional theory, we investigate the spin transport properties of molecular junction based on metal (Cu,Fe) phthalocyanines between V-shaped zigzag-edged graphene nanorribons. The results show that the electronic transport properties mainly depend on the center transition metal. The negative differential resistance behaviors and spin splitting phenomenon can be observed.
    Keywords: ATK, Application, spintronics, graphene, nanoribbon
    Area: graphene
    BibTeX:
    @article{Cui2014,
      author = {Cui, Liling and Yang, Bingchu and Li, Xinmei and He, Jun and Long, Mengqiu},
      title = {Electronic transport properties of transition metal (Cu, Fe) phthalocyanines connecting to V-shaped zigzag graphene nanoribbons},
      journal = {International Journal of Modern Physics B},
      publisher = {World Scientific Pub Co Pte Lt},
      year = {2014},
      volume = {28},
      number = {08},
      pages = {1450019},
      doi = {http://dx.doi.org/10.1142/s0217979214500192}
    }
    
    Zhongkai Huang, Jinfeng Qu, Xiangyang Peng, Wenliang Liu, Kaiwang Zhang, Xiaolin Wei & Jianxin Zhong Quantum confinement in graphene quantum dots 2014 Physica Status Solidi (Rapid Research Letters)
    Vol. 8(5), 436-440 
    DOI  
    Abstract: By performing density functional theory calculations, we studied the quantum confinement in charged graphene quantum dots (GQDs), which is found to be clearly edge and shape dependent. It is found that the excess charges have a large distribution at the edges of the GQD. The resulting energy spectrum shift is very nonuniform and hence the Coulomb diamonds in the charge stability diagram vary irregularly, in good agreement with the observed nonperiodic Coulomb blockade oscillation. We also illustrate that the level statistics of the GQDs can be described by a Gaussian distribution, as predicted for chaotic Dirac billiards. The charge stability diagram (left) and the Gaussian distribution of the width of the Coulomb diamonds (right), indicating the nonperiodic Coulomb blockade oscillation in GQD due to quantum confinement.
    Keywords: ATK, Application, graphene quantum dots, quantum confinement, density functional theory, edges, shapes
    Area: graphene
    BibTeX:
    @article{Huang2014,
      author = {Huang, Zhongkai and Qu, Jinfeng and Peng, Xiangyang and Liu, Wenliang and Zhang, Kaiwang and Wei, Xiaolin and Zhong, Jianxin},
      title = {Quantum confinement in graphene quantum dots},
      journal = {Physica Status Solidi (Rapid Research Letters)},
      publisher = {WILEY-VCH Verlag},
      year = {2014},
      volume = {8},
      number = {5},
      pages = {436--440},
      doi = {http://dx.doi.org/10.1002/pssr.201409064}
    }
    
    Muhammad R. Islam, Narae Kang, Udai Bhanu, Hari P. Paudel, Mikhail Erementchouk, Laurene Tetard, Michael N. Leuenberger & Saiful I. Khondakera Electrical property tuning via defect engineering of single layer MoS2 by oxygen plasma 2014 Nanoscale
    Vol. 6, 10033-10039 
    DOI URL 
    Abstract: We demonstrate that the electrical property of a single layer molybdenum disulfide (MoS2) can be significantly tuned from semiconducting to insulating regime via controlled exposure to oxygen plasma. The mobility, on-current and resistance of single layer MoS2 devices were varied up to four orders of magnitude by controlling the plasma exposure time. Raman spectroscopy, X-ray photoelectron spectroscopy and density functional theory studies suggest that the significant variation of electronic properties is caused by the creation of insulating MoO3-rich disordered domains in the MoS2 sheet upon oxygen plasma exposure, leading to an exponential variation of resistance and mobility as a function of plasma exposure time. The resistance variation calculated using an effective medium model is in excellent agreement with the measurements. The simple approach described here can be used for the fabrication of tunable two dimensional nanodevices on MoS2 and other transition metal dichalcogenides.
    Keywords: ATK, Application, Molybdenum disulfide, 2D material, TMDC, electronic transport, oxygen plasma, molybdenum trioxide
    Area: graphene
    BibTeX:
    @article{Islam2014,
      author = {Muhammad R. Islam and Narae Kang and Udai Bhanu and Hari P. Paudel and Mikhail Erementchouk and Laurene Tetard and Michael N. Leuenberger and Saiful I. Khondakera},
      title = {Electrical property tuning via defect engineering of single layer MoS2 by oxygen plasma},
      journal = {Nanoscale},
      year = {2014},
      volume = {6},
      pages = {10033-10039},
      url = {http://arxiv.org/ftp/arxiv/papers/1404/1404.5089.pdf},
      doi = {http://dx.doi.org/10.1039/C4NR02142H}
    }
    
    Josef Nahlik, Jan Voves, Alexandr Laposa & Jiri Kroutil The Study of Graphene Gas Sensor 2014 Key Engineering Materials
    Vol. 605, 495-498 
    DOI URL 
    Abstract: The graphene is suitable for gas sensing applications for its two dimensional char-acter which gives the best possible ratio between sensor surface and volume. The interaction between graphene surface and gas molecules can signicantly change the graphene layer trans-port properties. Therefore graphene can serve as a sensitive layer in a gas sensor. This work isconcentrated on the analysis of the conductivity of graphene layer exposed to different gases(NH3, CO2 ...). Together with the electrical measurement on the interdigital graphene sensora simulation based on quantum atomistic approach has been performed. We used ATK toolkitby Quantuwise based on density functional theory (DFT) models. The exchange-correlationpotential is approximated within the generalized gradient approximation (GGA). The trans-port properties of the electrode-device- electrode geometry were calculated by means of non-equilibrium Greens function formalism as implemented in ATK. Experimental conductivitychanges are compared with the simulation results.
    Keywords: ATK, Application
    Area: graphene
    BibTeX:
    @article{Nahlik2014,
      author = {Josef Nahlik and Jan Voves and Alexandr Laposa and Jiri Kroutil},
      title = {The Study of Graphene Gas Sensor},
      journal = {Key Engineering Materials},
      year = {2014},
      volume = {605},
      pages = {495-498},
      url = {http://www.scientific.net/KEM.605.495},
      doi = {http://dx.doi.org/10.4028/www.scientific.net/KEM.605.495}
    }
    
    Shenglin Peng, Zhixiong Yang, Xiang Ni, Hua Zhang, Jun Ouyang & Ouyang Fangping DNA translocation through graphene nanopores: a first-principles study 2014 Materials Research Express
    Vol. 1(1), 015044 
    URL 
    Abstract: With first-principles transport simulation, a biosensor device built from a graphene nanoribbon containing a nanopore is designed for DNA sequencing. The four DNA nucleobases can be distinguished from one another by detecting the transverse-currents of this device. To investigate the transport properties and mechanisms of such a device, we examine the motion effects of nucleobases. The analysis of the transmission spectra and frontier orbital energy shows that the transverse-currents variation of the device strongly results from the long-range interaction between nucleobases and the device. This interaction makes transverse-currents ultra-sensitive to the molecule inside the pore. By rotating the nucleotides inside the pore, the transverse-currents of the device vary along with the changes of molecular orientation. Due to the long-range interaction, when nucleobases chain translocates through nanopore of the device, the influences of adjacent nucleobases on transverse-currents cannot be ignored. These novel effects of nucleobases on the transport capacity of the device provide some theoretical guidance for the design of graphene-based nanopore sensor devices.
    Keywords: ATK, Application, DNA, nanopores
    Area: graphene
    BibTeX:
    @article{Peng2014,
      author = {Shenglin Peng and Zhixiong Yang and Xiang Ni and Hua Zhang and Jun Ouyang and Ouyang Fangping},
      title = {DNA translocation through graphene nanopores: a first-principles study},
      journal = {Materials Research Express},
      year = {2014},
      volume = {1},
      number = {1},
      pages = {015044},
      url = {http://stacks.iop.org/2053-1591/1/i=1/a=015044}
    }
    
    Qing Peng, Albert K. Dearden, Jared Crean, Liang Han, Sheng Liu, Xiaodong Wen & Suvranu De New materials graphyne, graphdiyne, graphone, and graphane: review of properties, synthesis, and application in nanotechnology 2014 Nanotechnology, Science and Applications
    Vol. 7, 1 
    DOI  
    Abstract: Plenty of new two-dimensional materials including graphyne, graphdiyne, graphone, and graphane have been proposed and unveiled after the discovery of the "wonder material" graphene. Graphyne and graphdiyne are two-dimensional carbon allotropes of graphene with honeycomb structures. Graphone and graphane are hydrogenated derivatives of graphene. The advanced and unique properties of these new materials make them highly promising for applications in next generation nanoelectronics. Here, we briefly review their properties, including structural, mechanical, physical, and chemical properties, as well as their synthesis and applications in nanotechnology. Graphyne is better than graphene in directional electronic properties and charge carriers. With a band gap and magnetism, graphone and graphane show important applications in nanoelectronics and spintronics. Because these materials are close to graphene and will play important roles in carbon-based electronic devices, they deserve further, careful, and thorough studies for nanotechnology applications.
    Keywords: ATK, Application, two-dimensional materials, graphene-like structures, properties and synthesis, nanotechnology applications, graphyne, hydrogenation of graphene, Review
    Area: graphene
    BibTeX:
    @article{Peng2014c,
      author = {Peng, Qing and Dearden, Albert K. and Crean, Jared and Han, Liang and Liu, Sheng and Wen, Xiaodong and De, Suvranu},
      title = {New materials graphyne, graphdiyne, graphone, and graphane: review of properties, synthesis, and application in nanotechnology},
      journal = {Nanotechnology, Science and Applications},
      publisher = {Dove Medical Press Ltd.},
      year = {2014},
      volume = {7},
      pages = {1},
      doi = {http://dx.doi.org/10.2147/nsa.s40324}
    }
    
    K. Bikshalu, M.V. Manasa, V.S.K. Reddy, P.C.S. Reddy & K. Venkateswara Rao Comparison of Atomic Level Simulation Studies of MOSFETs Containing Silica and Lantana Nanooxide Layers 2013 Journal of Nano- And Electronic Physics
    Vol. 5(4), 04058 
    URL 
    Abstract: The intense downscaling of a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) to nano range for improving the device performance requires a high-k dielectric material instead of conventional silica (SiO2) as to avoid Quantum Mechanical Tunneling towards the gate terminal which leads to unnecessary gate current. Out of all the rare earth oxide materials, since lanthana (La2O3) has significantly high dielectric constant (k) and bandgap, we've chosen it as oxide layer for one of the MOSFETs. In this work, we simulated two MOSFETs - one with nano SiO2 oxide layer and other with nano La2O3 oxide layer in the atomic level to analyze and compare the transmission spectra, I-V characteristics and Channel conductance of both the MOSFETs.
    Keywords: ATK, Application, MOSFET, Nano oxide layer, Quantum mechanical tunneling, Transmission spectra, I-V characterischar, Channel conductance
    Area: semi
    BibTeX:
    @article{Bikshalu2013,
      author = {K. Bikshalu and M.V. Manasa and V.S.K. Reddy and P.C.S. Reddy and K. Venkateswara Rao},
      title = {Comparison of Atomic Level Simulation Studies of MOSFETs Containing Silica and Lantana Nanooxide Layers},
      journal = {Journal of Nano- And Electronic Physics},
      year = {2013},
      volume = {5},
      number = {4},
      pages = {04058},
      url = {http://jnep.sumdu.edu.ua/en/component/content/full_article/1135}
    }
    
    Yongqing Cai, Zhaoqiang Bai, Hui Pan, Yuan Ping Feng, Boris I. Yakobson & Yong-Wei Zhang Constructing metallic nanoroads on a MoS2 monolayer via hydrogenation 2014 Nanoscale
    Vol. 6(3), 1691-1697 
    DOI  
    Abstract: Monolayer transition metal dichalcogenides recently emerged as a new family of two-dimensional materials potentially suitable for numerous applications in electronic and optoelectronic devices due to the presence of a finite band gap. Many proposed applications require efficient transport of charge carriers within these semiconducting monolayers. However, constructing a stable conducting nanoroad on these atomically thin semiconductors is still a challenge. Here we demonstrate that hydrogenation on the surface of a MoS2 monolayer induces a semiconductor-metal transition, and strip-patterned hydrogenation is able to generate a conducting nanoroad. The band-gap closing arises from the formation of in-gap hybridized states mainly consisting of Mo 4d orbitals, as well as the electron donation from hydrogen to the lattice host. Ballistic conductance calculations reveal that such a nanoroad on the MoS2 surface exhibits an integer conductance, indicating small carrier scattering, and thus is ideal for serving as a conducting channel or an interconnect without compromising the mechanical and structural integrity of the monolayer.
    Keywords: ATK, Application, MoS2, conductance
    Area: nanotubes
    BibTeX:
    @article{Cai2014,
      author = {Cai, Yongqing and Bai, Zhaoqiang and Pan, Hui and Feng, Yuan Ping and Yakobson, Boris I. and Zhang, Yong-Wei},
      title = {Constructing metallic nanoroads on a MoS2 monolayer via hydrogenation},
      journal = {Nanoscale},
      publisher = {Royal Society of Chemistry (RSC)},
      year = {2014},
      volume = {6},
      number = {3},
      pages = {1691-1697},
      doi = {http://dx.doi.org/10.1039/c3nr05218d}
    }
    
    Valentina Cauda, Paolo Motto, Denis Perrone, Gianluca Piccinini & Danilo Demarchi pH-triggered conduction of amine-functionalized single ZnO wire integrated on a customized nanogap electronic platform 2014 Nanoscale Research Letters
    Vol. 9Nanoscale Research Letters, 53 
    DOI URL 
    Abstract: The electrical conductance response of single ZnO microwire functionalized with amine-groups was tested upon an acid pH variation of a solution environment after integration on a customized gold electrode array chip. ZnO microwires were easily synthesized by hydrothermal route and chemically functionalized with aminopropyl groups. Single wires were deposited from the solution and then oriented through dielectrophoresis across eight nanogap gold electrodes on a platform single chip. Therefore, eight functionalized ZnO microwire-gold junctions were formed at the same time, and being integrated on an ad hoc electronic platform, they were ready for testing without any further treatment. Experimental and simulation studies confirmed the high pH-responsive behavior of the amine-modified ZnO-gold junctions, obtaining in a simple and reproducible way a ready-to-use device for pH detection in the acidic range. We also compared this performance to bare ZnO wires on the same electronic platform, showing the superiority in pH response of the amine-functionalized material.
    Keywords: ATK, Application, ZnO wire; Aminopropyl functionalization; Nanogap electrodes; pH-responsive behavior; Gold-ZnO-gold
    Area: nanowires
    BibTeX:
    @article{Cauda2014,
      author = {Valentina Cauda and Paolo Motto and Denis Perrone and Gianluca Piccinini and Danilo Demarchi},
      title = {pH-triggered conduction of amine-functionalized single ZnO wire integrated on a customized nanogap electronic platform},
      booktitle = {Nanoscale Research Letters},
      journal = {Nanoscale Research Letters},
      year = {2014},
      volume = {9},
      pages = {53},
      url = {http://www.nanoscalereslett.com/content/pdf/1556-276X-9-53.pdf},
      doi = {http://dx.doi.org/10.1186/1556-276X-9-53}
    }
    
    Yao-Jun Dong, Xue-Feng Wang, P. Vasilopoulos, Ming-Xing Zhai & Xue-Mei Wu Half-metallicity in aluminum-doped zigzag silicene nanoribbons 2014 Journal of Physics D: Applied Physics
    Vol. 47(10), 105304 
    DOI  
    Abstract: The spin-dependent electronic structures of aluminum-(Al) doped zigzag silicene nanoribbons (ZSiNRs) are investigated by first-principles calculations. When ZSiNRs are substitutionally doped by a single Al atom on different sites in every three primitive cells, they become half-metallic in some cases, a property that can be used in spintronic devices. More interestingly, spin-down electrons can be transported at the Fermi energy when the Al atom is placed on the sub-edge site. In contrast, spin-up electrons can be transported at the Fermi energy when the ZSiNRs are doped on sites near their centre. The magnetic moment on the edge is considerably suppressed if the Al atom is doped on edge or near-edge sites. Similar results are obtained for a phosphorus-(P) and boron-(B) doped ZSiNR. When two or more Si atoms are replaced by Al atoms, in general the half-metallic behaviour is replaced by a metallic, spin gapless semiconducting or semiconducting one. When a line of six Si atoms, along the ribbon's width, are replaced by Al atoms, the spin resolution of the band structure is suppressed and the system becomes nonmagnetic.
    Keywords: ATK, Application, nanoribbon, doping, silicene
    Area: graphene
    BibTeX:
    @article{Dong2014,
      author = {Yao-Jun Dong and Xue-Feng Wang and P. Vasilopoulos and Ming-Xing Zhai and Xue-Mei Wu},
      title = {Half-metallicity in aluminum-doped zigzag silicene nanoribbons},
      journal = {Journal of Physics D: Applied Physics},
      year = {2014},
      volume = {47},
      number = {10},
      pages = {105304},
      doi = {http://dx.doi.org/10.1088/0022-3727/47/10/105304}
    }
    
    Ramon Gomez-Aguilar & Jaime Ortiz-Lopez First principle studies of charge transport in PPV polymer under conformational deformation 2014 Journal of Polymer Science Part B: Polymer Physics
    Vol. 52(8), 578 
    DOI  
    Abstract: We consider the inclusion of torsional deformations in the structure of an infinite chain of poly-p-phenylene vinylene and study the consequences on charge transport along the polymer length. Calculations of the electronic transport are performed with density functional theory combined with Keldysh nonequilibrium Green's function method. Deformations are modeled either as a sharp rotation of the polymer backbone about a single chemical bond or as a continuous twist extending along various monomer units. We study current-voltage (I-V) characteristics in a two probe configuration as a function of angle and degree of torsional sharpness and demonstrate that when the backbone torsion is abrupt a barrier to electron transport builds up that becomes maximum at an angle of 100°. The outcome of our calculations is that the abrupt twist of the polymer backbone creates two virtually disconnected segments, which validates models that treat a real polymer as distribution of chains of different sizes and conjugation lengths.
    Keywords: ATK, Application, charge transport, computer modeling, conformational deformation, conjugated polymers
    Area: molecular electronics
    BibTeX:
    @article{Gomez-Aguilar2014,
      author = {Gomez-Aguilar, Ramon and Ortiz-Lopez, Jaime},
      title = {First principle studies of charge transport in PPV polymer under conformational deformation},
      journal = {Journal of Polymer Science Part B: Polymer Physics},
      year = {2014},
      volume = {52},
      number = {8},
      pages = {578},
      doi = {http://dx.doi.org/10.1002/polb.23454}
    }
    
    Yan-Dong Guo, Xiao-Hong Yan & Yang Xiao The spin-dependent transport of Co-encapsulated Si nanotubes contacted with Cu electrodes 2014 Applied Physics Letters
    Vol. 104(6), 063103 
    DOI  
    Abstract: Unlike carbon nanotubes, silicon ones are hard to form. However, they could be stabilized by metal-encapsulation. Using first-principles calculations, we investigate the spin-dependent electronic transport of Co-encapsulated Si nanotubes, which are contacted with Cu electrodes. For the finite tubes, as the tube-length increases, the transmission changes from spin-unpolarized to spin-polarized. Further analysis shows that, not only the screening of electrodes on Co's magnetism but also the spin-asymmetric Co-Co interactions are the physical mechanisms. As Cu and Si are the fundamental elements in semiconductor industry, our results may throw light on the development of silicon-based spintronic devices.
    Keywords: ATK, Application, spin-dependent transport, nanotubes
    Area: nanotubes, spin
    BibTeX:
    @article{Guo2014a,
      author = {Guo, Yan-Dong and Yan, Xiao-Hong and Xiao, Yang},
      title = {The spin-dependent transport of Co-encapsulated Si nanotubes contacted with Cu electrodes},
      journal = {Applied Physics Letters},
      year = {2014},
      volume = {104},
      number = {6},
      pages = {063103},
      doi = {http://dx.doi.org/10.1063/1.4865589}
    }
    
    Rupan Preet Kaur, Ravinder Singh Sawhney & Derick Engles Asymmetrical Molecular Junctions with Different Alligator Clips 2013 International Journal of Materials Science and Engineering
    Vol. 1(2), 112 
    DOI  
    Abstract: This paper describes different molecular junctions with different alligator clips connected to gold electrodes at nanometre-scale. Our objective was to determine the charge transport characteristics of these junctions and determine the optimum alligator clip pair. We scrutinised anthracenedithiol (ADT), anthracenediamine (ADA) and anthracenethiolamine (ATA) and computed their conductance parameters through our simulations via Semi Emperical Extended Huckel Theory Approach. We aimed at finding that whether symmetrical (same alligator clips at each side) or asymmetrical (different alligator clips at each side) is the optimised approach to connect the anthracene molecule with gold electrodes and found that different alligator clips i.e. thiol and amine exhibited more conduction than that of same clip pair i.e. ADT and ADA. We further examined the effect of changing alligator clips positions from para to meta and found varied quantum interference effects. Peak to valley current ratios (PVR) for ADT was found to be maximum as 7.05 whereas meta ATA exhibited lowest peak to valley current ratio of 1.44.
    Keywords: ATK, Application, molecular junction
    Area: molecular electronics
    BibTeX:
    @article{Kaur2013a,
      author = {Kaur, Rupan Preet and Sawhney, Ravinder Singh and Engles, Derick},
      title = {Asymmetrical Molecular Junctions with Different Alligator Clips},
      journal = {International Journal of Materials Science and Engineering},
      publisher = {Engineering and Technology Publishing},
      year = {2013},
      volume = {1},
      number = {2},
      pages = {112},
      doi = {http://dx.doi.org/10.12720/ijmse.1.2.112-117}
    }
    
    Yusuke Nakai, Kazuya Honda, Kazuhiro Yanagi, Hiromichi Kataura, Teppei Kato, Takahiro Yamamoto & Yutaka Maniwa Giant Seebeck coefficient in semiconducting single-wall carbon nanotube film 2014 Applied Physics Express
    Vol. 7, 025103 
    DOI  
    Abstract: We found a giant Seebeck effect in semiconducting single-wall carbon nanotube (SWCNT) films, which exhibited a performance comparable to that of commercial Bi2Te3 alloys. Carrier doping of semiconducting SWCNT films further improved the thermoelectric performance. These results were reproduced well by first-principles transport simulations based on a simple SWCNT junction model. These findings suggest strategies that pave the way for emerging printed, all-carbon, flexible thermoelectric devices.
    Keywords: ATK, Application, Seebeck coefficient, carbon nanotube
    Area: nanotubes, thermo
    BibTeX:
    @article{Nakai2014,
      author = {Yusuke Nakai and Kazuya Honda and Kazuhiro Yanagi and Hiromichi Kataura and Teppei Kato and Takahiro Yamamoto and Yutaka Maniwa},
      title = {Giant Seebeck coefficient in semiconducting single-wall carbon nanotube film},
      journal = {Applied Physics Express},
      year = {2014},
      volume = {7},
      pages = {025103},
      doi = {http://dx.doi.org/10.7567/APEX.7.025103}
    }
    
    Fangping Ouyang, Zhixiong Yang, Xiang Ni, Nannan Wu, Yu Chen & Xiang Xiong Hydrogenation-induced edge magnetization in armchair MoS2 nanoribbon and electric field effects 2014 Applied Physics Letters
    Vol. 104(7), 071901 
    DOI  
    Abstract: We performed density functional theory study on the electronic and magnetic properties of armchair MoS2 nanoribbons (AMoS2NR) with different edge hydrogenation. Although bare and fully passivated AMoS2NRs are nonmagnetic semiconductors, it was found that hydrogenation in certain patterns can induce localized ferromagnetic edge state in AMoS2NRs and make AMoS2NRs become antiferromagnetic semiconductors or ferromagnetic semiconductors. Electric field effects on the bandgap and magnetic moment of AMoS2NRs were investigated. Partial edge hydrogenation can change a small-sized AMoS2NR from semiconductor to metal or semimetal under a moderate transverse electric field. Since the rate of edge hydrogenation can be controlled experimentally via the temperature, pressure and concentration of H2, our results suggest edge hydrogenation is a useful method to engineer the band structure of AMoS2NRs.
    Keywords: ATK, Application,magnetization, MoS2, nanoribbon
    Area: graphene
    BibTeX:
    @article{Ouyang2014a,
      author = {Ouyang, Fangping and Yang, Zhixiong and Ni, Xiang and Wu, Nannan and Chen, Yu and Xiong, Xiang},
      title = {Hydrogenation-induced edge magnetization in armchair MoS2 nanoribbon and electric field effects},
      journal = {Applied Physics Letters},
      year = {2014},
      volume = {104},
      number = {7},
      pages = {071901},
      doi = {http://dx.doi.org/10.1063/1.4865902}
    }
    
    Pankaj Srivastava, Neeraj K. Jaiswal & Gagan Kant Tripathi Chlorine sensing properties of zigzag boron nitride nanoribbons 2014 Solid State Communications
    Vol. 185, 41 
    DOI  
    Abstract: Abstract The density functional theory based first-principles calculations have been employed to explore the chlorine sensing properties of zigzag boron nitride nanoribbons (ZBNNR). The sensing was investigated by calculating electronic structures and current-voltage (I-V) behavior. Three different possibilities were considered for the chlorine adsorption on ZBNNR and the findings were compared with bare ribbons. It is revealed that presence of chlorine has a profound effect on the electronic and transport properties of ZBNNR. Bare ZBNNR are half-metallic in nature whereas chlorine adsorption turns them semiconducting irrespective of adsorption site. Further, the negative differential resistance has been observed in bare ribbons which disappear upon the chlorine adsorption. Enhanced sensing capability is predicted when chlorine is attached at the N edge or at both the edges of the ZBNNR.
    Keywords: ATK, Application, boron nitride, nanoribbon
    Area: graphene
    BibTeX:
    @article{Srivastava2014f,
      author = {Pankaj Srivastava and Neeraj K. Jaiswal and Gagan Kant Tripathi},
      title = {Chlorine sensing properties of zigzag boron nitride nanoribbons},
      journal = {Solid State Communications },
      year = {2014},
      volume = {185},
      pages = {41},
      doi = {http://dx.doi.org/10.1016/j.ssc.2014.01.009}
    }
    
    Zilai Yan, Xiang Xiong, Yu Chen & Fangp Ouyang Heterostructural bilayers of graphene and molybdenum disulfide: Configuration types, band opening and enhanced light response 2014 Superlattices and Microstructures
    Vol. 68, 56 - 65 
    DOI  
    Abstract: The properties of graphene absorption on graphene-like material can be modulated by the stacking arrangement. Here, we propose a "least squares" classification method for analyzing configuration types of graphene/molybdenum disulfide heterobilayers (G/MoS2 HBLs) while binding energy, electronic structure and optical absorption of G/MoS2 HBLs are investigated via first principles calculations. Owing to the lattice mismatch, no traditional Å and AB stacking exist but AA- and AB-stacking-like configurations have been found. Paradoxically, AB-stacking-like configuration, generally as the most stable stacking sequence, does not correspond to the relaxed structure. We interpret this paradox in terms of graphene corrugation. A detailed analysis of the electronic structure indicates that bandgaps of all configurations types (types of G/MoS2 HBLs) are opened and tunable under the different interlayer distance. Furthermore, compared with monolayer MoS2, G/MoS2 HBLs display an enhanced light response, a promising feature for photocatalytic applications.
    Keywords: ATK, Application, graphene, molybdenum disulfide, bilayer
    Area: graphene
    BibTeX:
    @article{Yan2014,
      author = {Zilai Yan and Xiang Xiong and Yu Chen and Fangp Ouyang},
      title = {Heterostructural bilayers of graphene and molybdenum disulfide: Configuration types, band opening and enhanced light response },
      journal = {Superlattices and Microstructures},
      year = {2014},
      volume = {68},
      pages = {56 - 65},
      doi = {http://dx.doi.org/10.1016/j.spmi.2014.01.013}
    }
    
    Shen-Lang Yan, Meng-Qiu Long, Xiao-Jiao Zhang & Hui Xu The effects of spin-filter and negative differential resistance on Fe-substituted zigzag graphene nanoribbons 2014 Physics Letters A
    Vol. 378(13), 960 - 965 
    DOI  
    Abstract: Using the first-principle calculations, we investigate the spin-dependent transport properties of Fe-substituted zigzag graphene nanoribbons (ZGNRs). The substituted ZGNRs with single or double Fe atoms, distributing symmetrically or asymmetrically on both edges, are considered. Our results show Fe-substitution can significantly change electronic transport of ZGNRs, and the spin-filter effect and negative differential resistance (NDR) can be observed. We propose that the distribution of the electronic spin-states of ZGNRs can be modulated by the substituted Fe and results in the spin-polarization, and meanwhile the change of the delocalization of the frontier molecular orbitals at different bias may be responsible for the NDR behavior.
    Keywords: ATK, Application, graphene, nanoribbon
    Area: graphene
    BibTeX:
    @article{Yan2014b,
      author = {Shen-Lang Yan and Meng-Qiu Long and Xiao-Jiao Zhang and Hui Xu},
      title = {The effects of spin-filter and negative differential resistance on Fe-substituted zigzag graphene nanoribbons },
      journal = {Physics Letters A},
      year = {2014},
      volume = {378},
      number = {13},
      pages = {960 - 965},
      doi = {http://dx.doi.org/10.1016/j.physleta.2014.01.042}
    }
    
    Shundong Yuan, Shiyan Wang, Qunbo Mei, Qidan Ling, Lianhui Wang & Wei Huang Effects of Electrodes and Nitrogen-Atom Locations on Electron Transport in C59N Molecular Junctions: A First-Principles Study 2014 Journal of Physical Chemistry C
    Vol. 118(1), 617-626 
    DOI  
    Abstract: The electron-transport properties of C59N molecular junctions with different electrodes (Au, Al, and CNT) are investigated by density functional theory (DFT) combined with the first-principle nonequilibrium Green's function (NEGF). The current-voltage characteristics of all the models are calculated. The results show both electrode species and nitrogen-atom location may affect the transport properties of the C59N molecular junction. When the nitrogen atom of the C59N molecule is located close to one side of the junction, the rectifying behavior can be found in CNT-electrode models, while there is no observable rectification in metal-electrode models. The negative differential resistance may be observed in the C59N molecular junction using CNT electrodes when the nitrogen atom is at a certain location. The results are discussed through examining the transmission spectra, the molecular projected self-consistent Hamiltonian states, and the projection of the density of states.
    Keywords: ATK, Application, electron transport, molecular junction
    Area: molecular electronics
    BibTeX:
    @article{Yuan2014a,
      author = {Yuan, Shundong and Wang, Shiyan and Mei, Qunbo and Ling, Qidan and Wang, Lianhui and Huang, Wei},
      title = {Effects of Electrodes and Nitrogen-Atom Locations on Electron Transport in C59N Molecular Junctions: A First-Principles Study},
      journal = {Journal of Physical Chemistry C},
      year = {2014},
      volume = {118},
      number = {1},
      pages = {617-626},
      doi = {http://dx.doi.org/10.1021/jp407395d}
    }
    
    H. Zhao, Y.Q. Xu, W.K. Zhao, K. Gao & D.S. Liu Electronic transport properties of indolyl spirooxazine/merooxazine-based light-driven molecular switch: The effect of amino/nitro substituents 2014 Physica B: Condensed Matter
    Vol. 437, 41 
    DOI  
    Abstract: Abstract By applying non-equilibrium Green's function formulation combined with first-principles density functional theory, we explore the electronic transport properties of indolinospironaphthoxazine (SO)/indolinomeronaphthoxazine (MO). The results indicate that the MO allows a far larger current than the SO. The substituent group can cause shifts of the energy levels. Higher ON/OFF current ratio can be obtained if either amino or nitro substituent is placed at the position of naphthalene moiety. Our results suggest that such molecular wires can generally display switching function and the efficiency can be increased by adding certain substituent groups to the molecules.
    Keywords: ATK, Application, Molecular electronics, molecular switch
    Area: molecular electronics
    BibTeX:
    @article{Zhao2014a,
      author = {H. Zhao and Y.Q. Xu and W.K. Zhao and K. Gao and D.S. Liu},
      title = {Electronic transport properties of indolyl spirooxazine/merooxazine-based light-driven molecular switch: The effect of amino/nitro substituents },
      journal = {Physica B: Condensed Matter},
      year = {2014},
      volume = {437},
      pages = {41},
      doi = {http://dx.doi.org/10.1016/j.physb.2013.12.027}
    }
    
    Yan-Dong Guo, Xiao-Hong Yan & Yang Xiao Electrical control of spin polarization of conductance in Mn-encapsulated Si nanotube 2014 Applied Physics Express
    Vol. 7(7), 075001 
    DOI  
    Abstract: Compared with the use of magnetic methods, electrical manipulation of the spin polarization of a current could greatly reduce the devices' dimensions and energy consumption. Using first-principles calculations, the spin-dependent electronic transport of a Mn-encapsulated Si nanotube contacted with Cu electrodes is investigated. As the gate voltage decreases, the conductance changes from spin unpolarized to spin polarized (the polarization could reach 90%). Electron transfer between Si and Mn atoms modulated by the gate voltage is found to be the physical mechanism. Because Si and Cu are fundamental materials in integrated circuits, these findings may be quite useful for developing Si-based spintronic devices.
    Keywords: ATK; Application; nanotube
    Area: nanotubes
    BibTeX:
    @article{Guo2014,
      author = {Yan-Dong Guo and Xiao-Hong Yan and Yang Xiao},
      title = {Electrical control of spin polarization of conductance in Mn-encapsulated Si nanotube},
      journal = {Applied Physics Express},
      year = {2014},
      volume = {7},
      number = {7},
      pages = {075001},
      doi = {http://dx.doi.org/10.7567/APEX.7.075001}
    }
    
    M. Chakraverty, H.M. Kittur & P.A. Kumar First Principle Simulations of Various Magnetic Tunnel Junctions for Applications in Magnetoresistive Random Access Memories 2013 Nanotechnology, IEEE Transactions on
    Vol. 12(6)Nanotechnology, IEEE Transactions on, 971-977 
    DOI  
    Abstract: This paper reports the first principle simulations of Fe/MgO/Fe, Fe/Y2O3/Fe, Fe/HfO2/Fe, and Fe/Al2O3/Fe magnetic tunnel junctions (MTJs). From the device-level and circuit-level simulations carried out in this paper, the Fe/MgO/Fe configuration has been found to be the best. From the device-level simulations, all the four configurations of MTJs have been compared with regards to the bias dependence of tunnel magnetoresistance ratios (TMRs), insulator thickness dependence of TMR, and insulator thickness dependence of parallel and antiparallel state resistances. Finally, from the circuit-level simulations, the static and switching power dissipations have been computed along with the delay time estimation.
    Keywords: ATK, Application, hafnium compounds, iron, magnesium compounds, random-access storage, yttrium compounds, Fe-Al2O3-Fe, Fe-HfO2-Fe, Fe-MgO-Fe, Fe-Y2O3-Fe, antiparallel state resistances, circuit-level simulations, device-level simulations, insulator thickness dependence, magnetic tunnel junctions, magnetoresistive random access memories, tunnel magnetoresistance ratios, Atomic layer deposition, Insulators, Iron, Magnetic separation, Magnetic tunneling, Resistance, Tunneling magnetoresistance, Density functional theory (DFT), MRAM, local spin density approximation (LSDA), magnetic tunnel junction (MTJ)
    Area: interfaces; nvm; semi; spin
    BibTeX:
    @article{Chakraverty2013a,
      author = {Chakraverty, M. and Kittur, H.M. and Kumar, P.A.},
      title = {First Principle Simulations of Various Magnetic Tunnel Junctions for Applications in Magnetoresistive Random Access Memories},
      booktitle = {Nanotechnology, IEEE Transactions on},
      journal = {Nanotechnology, IEEE Transactions on},
      year = {2013},
      volume = {12},
      number = {6},
      pages = {971--977},
      doi = {http://dx.doi.org/10.1109/TNANO.2013.2274902}
    }
    
    Michiharu Tabe, Daniel Moraru, Earfan Hamid, Arup Samanta, Le The Anh, Takeshi Mizuno & Hiroshi Mizuta Dopant-Atom-Based Tunnel SOI-MOSFETs 2013 ECS Transactions
    Vol. 58(9), 89-95 
    DOI  
    Abstract: Recently, the role of dopants in Si devices has been changing after a long and successful history in Si integrated circuit technology. The change can be seen as a transition from "bulk-type" dopants, with averaged potential, to "atom-type" dopants, with individual atomistic potential. Furthermore, dopant energy levels are modified by the effect of dielectric misfit with surrounding Si and the outside structure, which leads to the transformation of conventional dopants into artificial deep dopants. This effect may be significantly important for the purpose of the extension of operation temperature range of dopant-atom devices from low temperatures (<50 K) to room temperature.
    Keywords: ATK; Application; silicon nanostructures; single donor; spectroscopy; transistor; channel; devices; donors; doping
    Area: semi
    BibTeX:
    @article{Tabe2013,
      author = {Tabe, Michiharu and Moraru, Daniel and Hamid, Earfan and Samanta, Arup and Anh, Le The and Mizuno, Takeshi and Mizuta, Hiroshi},
      title = {Dopant-Atom-Based Tunnel SOI-MOSFETs},
      journal = {ECS Transactions},
      year = {2013},
      volume = {58},
      number = {9},
      pages = {89--95},
      doi = {http://dx.doi.org/10.1149/05809.0089ecst}
    }
    
    Qiu-Hua Wu, Peng Zhao & De-Sheng Liu First-Principles Study of the Rectifying Properties of the Alkali-Metal-Atom-Doped BDC60 Molecule 2014 Acta Physico-Chimica Sinica
    Vol. 30(1), 53 
    DOI URL 
    Abstract: We investigated the effect of alkali-metal-atom doping on the electronic transport properties of BDC60 molecules, using a combination of first-principles density-functional theory and the non-equilibrium Green's function. Our calculation results show that alkali-metal-atom-doped BDC60 molecules exhibit good rectifying and negative differential resistance behaviors at very low bias. The intrinsic mechanisms for these phenomena are discussed systematically in terms of the transmission spectra and frontier molecular orbitals, as well as their spatial distributions under various external applied biases. Our study will help in developing future applications of BDC60 molecules in low-bias rectifying and negative differential resistance molecular devices.
    Keywords: ATK; Application; density functional theory; non-equilibrium Green's function; rectifying; negative differential resistance (NDR); electronic transport; negative differential resistance; single-C-60 transistor; transport-properties; diodes; C-60; rectification; encapsulation; rectifiers; nitrogen
    Area: molecular electronics; fullerenes
    BibTeX:
    @article{WUQiu-Hua2014,
      author = {Wu, Qiu-Hua and Zhao, Peng and Liu, De-Sheng},
      title = {First-Principles Study of the Rectifying Properties of the Alkali-Metal-Atom-Doped BDC60 Molecule},
      journal = {Acta Physico-Chimica Sinica},
      publisher = {Acta Phys. Chim. Sin.},
      year = {2014},
      volume = {30},
      number = {1},
      pages = {53},
      url = {http://www.whxb.pku.edu.cn/EN/abstract/article_28621.shtml},
      doi = {http://dx.doi.org/10.3866/PKU.WHXB201311081}
    }
    
    Zhi Yang, Baolong Zhang, Xuguang Liu, Xiuyan Li, Yongzhen Yang, Shijie Xiong & Bingshe Xu Size-dependent magnetic order and giant magnetoresistance in organic titanium-benzene multidecker cluster 2014 Phys. Chem. Chem. Phys.
    Vol. 16(5), 1902-1908 
    DOI  
    Abstract: Using density functional theory and non-equilibrium Green's function method, we investigated the magnetic and transport properties of small organic titanium-benzene sandwich clusters TinBzn+1 (n = 1-3). The results show that TiBz2 is nonmagnetic while Ti2Bz3 and Ti3Bz4 are ferromagnetic, and our prediction is in agreement with experimental observation. The double exchange mechanism plays a key role in the ferromagnetism of larger clusters. With Ni as the two electrodes, significant spin-filter efficiency (SFE) and giant magnetoresistance (GMR) were found in the TinBzn+1 molecular junction. These transport properties could be controlled by cluster size, bias voltage or gate voltage. Specially, a sign-reversible GMR effect was observed in the Ti2Bz3 molecular junction. Finally, the microscopic mechanisms of SFE and GMR were suggested.
    Keywords: ATK; Application; molecular electronics; rice-ball structures; sandwich clusters; transition-metals; decker-sandwich; gas-phase; complexes; spintronics
    Area: molecular electronics
    BibTeX:
    @article{Yang2014,
      author = {Yang, Zhi and Zhang, Baolong and Liu, Xuguang and Li, Xiuyan and Yang, Yongzhen and Xiong, Shijie and Xu, Bingshe},
      title = {Size-dependent magnetic order and giant magnetoresistance in organic titanium-benzene multidecker cluster},
      journal = {Phys. Chem. Chem. Phys.},
      publisher = {The Royal Society of Chemistry},
      year = {2014},
      volume = {16},
      number = {5},
      pages = {1902--1908},
      doi = {http://dx.doi.org/10.1039/C3CP54352H}
    }
    
    Yukihito Matsuura Tunnel current across linear homocatenated germanium chains 2014 Journal of Applied Physics
    Vol. 115(4), 043701 
    DOI  
    Abstract: The electronic transport properties of germanium oligomers catenating into linear chains (linear Ge chains) have been theoretically studied using first principle methods. The conduction mechanism of a Ge chain sandwiched between gold electrodes was analyzed based on the density of states and the eigenstates of the molecule in a two-probe environment. Like that of silicon chains (Si chains), the highest occupied molecular orbital of Ge chains contains the extended sigma-conjugation of Ge 4p orbitals at energy levels close to the Fermi level; this is in contrast to the electronic properties of linear carbon chains. Furthermore, the conductance of a Ge chain is expected to decrease exponentially with molecular length L. The decay constant beta, which is defined as exp(-beta*L), of a Ge chain is similar to that of a Si chain, whereas the conductance of the Ge chains is higher than that of Si chains even though the Ge-Ge bond length is longer than the Si-Si bond length.
    Keywords: ATK; Application; molecular electronics; elemental semiconductors; atomic chain
    Area: molecular electronics; semi; nanowire
    BibTeX:
    @article{Matsuura2014,
      author = {Matsuura, Yukihito},
      title = {Tunnel current across linear homocatenated germanium chains},
      journal = {Journal of Applied Physics},
      year = {2014},
      volume = {115},
      number = {4},
      pages = {043701},
      doi = {http://dx.doi.org/10.1063/1.4863118}
    }
    
    Jing Zeng & Ke-Qiu Chen Magnetic configuration dependence of magnetoresistance in a Fe-porphyrin-like carbon nanotube spintronic device 2014 Applied Physics Letters
    Vol. 104(3), 033104 
    DOI  
    Abstract: By using nonequilibrium Green's functions in combination with the density functional theory, we investigate the spin-dependent transport properties in a Fe-porphyrin-like carbon nanotube spintronic device. The results show that magnetoresistance ratio is strongly dependent on the magnetic configuration of the Fe-porphyrin-like carbon nanotube. Under the application of the external magnetic field, the magnetoresistance ratio of the device can be increased from about 19% to about 1020% by tuning the magnetic configuration in the device. Our results confirm that the magnetic configuration is a key factor for obtaining a high-performance spintronic device.
    Keywords: ATK; Application; molecular electronics; nanotubes; spintronics
    Area: molecular electronics; nanotubes; spin
    BibTeX:
    @article{Zeng2014,
      author = {Zeng, Jing and Chen, Ke-Qiu},
      title = {Magnetic configuration dependence of magnetoresistance in a Fe-porphyrin-like carbon nanotube spintronic device},
      journal = {Applied Physics Letters},
      year = {2014},
      volume = {104},
      number = {3},
      pages = {033104},
      doi = {http://dx.doi.org/10.1063/1.4862895}
    }
    
    N.N. Rusyaev & S.V. Spiridonov Nanowires defects, investigation of opportunity of early detection 2013 Vestnik Moskovskogo aviatsionnogo instituta
    Vol. 20(3) 
    URL 
    Abstract: This paper is devoted to investigation of possibility of defect detection in nanoconductors based on their transport property changes. The detection of nanodefects is a significant challenge, because it requires studying each individual sample along all stages of the engineering process. For effective checkout of the produced devices parameters there is a need for more fast, simple, and productive means for the defect detection. In this paper we investigate the possibility of detecting nanodefects according to their manifestation in the transport properties of a conductor. One of the possible types of such defects is the «conductor-defect-conductor» transition where the defect represents a suspended one- dimensional chain of atoms. The reason for studying defects of this type is rather high probability of emergence of such defects during operation under the mechanical or thermal impacts, and the possibility of occurrence of such defects in various manufacturing processes.

    The investigation was performed by mathematical modeling under Atomistix Virtual Nano Lab software. For the calculations we used two theoretical methods: EHT (Extended Huckel) and the method of Classic Potential. Based on these methods the models of defect-free and defective conductors were developed.

    The defect in these models was considered as an approximation to the model of a partial break of a conductor. The parameters for the comparative analysis included following characteristics: the difference of electron density, the difference of electrostatic potentials, molecular spectra, current-voltage curves. The measurements were performed on the two-electrode scheme with external voltage varying in the range from -2 to 2 V. Comparative analysis of the electronic structures and transport properties showed that there were differences sufficient enough for defect detection based on current-voltage characteristic changes.

    Nevertheless, it is necessary to keep in mind that we have investigated only one type of such nanodefects. In our case the defect conductive chain was considered to be perpendicular to main conductor side, and to have only methods for studying other types of defects.

    Keywords: ATK-SE; Application; nanowire; defects detection; conductors; transport properties; sensor
    Area: nanowires
    BibTeX:
    @article{Rusyaev2013,
      author = {Rusyaev, N. N. and Spiridonov, S. V.},
      title = {Nanowires defects, investigation of opportunity of early detection},
      journal = {Vestnik Moskovskogo aviatsionnogo instituta},
      year = {2013},
      volume = {20},
      number = {3},
      url = {http://www.mai.ru/science/vestnik/eng/publications.php?ID=44109&eng=Y}
    }
    
    Jichen Dong, Hui Li & Li Li Multi-functional nano-electronics constructed using boron phosphide and silicon carbide nanoribbons 2013 NPG Asia Mater
    Vol. 5, e56 
    DOI  
    Abstract: First-principles density functional theory and non-equilibrium Green function calculations provide theoretical support for the promising applications of multi-functional nano-electronics constructed using zigzag boron phosphide (BP) nanoribbons (zBPNRs) and silicon carbide nanoribbons (zSiCNRs). The results indicate that zBPNRs are non-magnetic direct bandgap semiconductors with bandgaps of ~1 eV. Devices constructed using hybrid zSiC-BP-SiC nanoribbon structures are found to exhibit not only significant field-effect characteristics but also tunable negative differential resistance. Moreover, Y- and Delta-shaped nano-structures composed of zBPNRs and zSiCNRs exhibit pronounced spin polarization properties at their edges, suggesting their potential use in spintronic applications. Interestingly, a transverse electric field can convert zBPNRs to non-magnetic indirect bandgap semiconductors, ferrimagnetic semiconductors or half-metals depending on the strength and direction of the field. This study may provide a new path for the exploration of nano-electronics.
    Keywords: ATK, Application, BP nanoribbons, density functional theory, hybrid structure, multi-functional nano-electronics, non-equilibrium Green Function, SiC nanoribbons
    Area: molecular electronics; 2dmat
    BibTeX:
    @article{Dong2013a,
      author = {Dong, Jichen and Li, Hui and Li, Li},
      title = {Multi-functional nano-electronics constructed using boron phosphide and silicon carbide nanoribbons},
      journal = {NPG Asia Mater},
      publisher = {Nature Japan KK},
      year = {2013},
      volume = {5},
      pages = {e56},
      doi = {http://dx.doi.org/10.1038/am.2013.31}
    }
    
    S. Sivasathya & D. John Thiruvadigal Ab Initio Study of Electron Transport Properties in Single Wall Carbon Nanotubes Connected with Different Metallic Electrodes 2013 Journal of Computational and Theoretical Nanoscience
    Vol. 10(10), 2391-2397 
    DOI  
    Abstract: We report the transport behaviour and evaluate the contact resistance on electrical conductance of an open-end metallic single wall carbon nanotube with and without local structural defects connected with metal interfaces like Copper (Cu), Gold (Au) and Silver (Ag) using the non-equilibrium Green's functions approach together with the density functional theory (DFT). The transmission spectra and the projected density of states for the devices such as Cu-CNT-Cu, Au-CNT-Au and Ag-CNT-Ag are compared with and without inclusion of defects. Ag-CNT-Ag has been observed to possess the maximum electron transport. We found that the Stone-Wales defect has almost negligible impact on the electrical performance compared to the monovacancy defect of single wall carbon nanotube (3, 3) and its junction with the metal electrodes at the Fermilevel. The Current-Voltage (I-V) characteristics of the devices are studied using the generalized Landauer-Buttiker formalism, from which the contact resistance is determined under low bias condition. Our results indicate that the contact resistance between the metal electrodes and a single wall carbon nanotube decreases in the order given by Cu > Au > Ag interfaces.
    Keywords: ATK, Application, contact resistance, density functional theory, I-V characteristics, monovacany, single wall carbon nanotube, Stone-Wales defects, transport properties, quantum-mechanics, defects, conductance
    Area: nanotubes
    BibTeX:
    @article{Sivasathya2013a,
      author = {Sivasathya, S. and Thiruvadigal, D. John},
      title = {Ab Initio Study of Electron Transport Properties in Single Wall Carbon Nanotubes Connected with Different Metallic Electrodes},
      journal = {Journal of Computational and Theoretical Nanoscience},
      year = {2013},
      volume = {10},
      number = {10},
      pages = {2391--2397},
      doi = {http://dx.doi.org/10.1166/jctn.2013.3220}
    }
    
    K.I. Doig, F. Aguesse, A.K. Axelsson, N.M. Alford, S. Nawaz, V.R. Palkar, S.P.P. Jones, R.D. Johnson, R.A. Synowicki & J. Lloyd-Hughes Coherent magnon and acoustic phonon dynamics in tetragonal and rare-earth-doped BiFeO3 multiferroic thin films 2013 Physical Review B
    Vol. 88(9), 094425 
    DOI  
    Abstract: Coherent magnons and acoustic phonons were impulsively excited and probed in thin films of the room temperature multiferroic Bi(1-x-y)Dy(x)La(y)FeO3 using femtosecond laser pulses. The elastic moduli of rhombohedral, tetragonal, and rare-earth doped BiFeO3 were determined from acoustic-mode frequencies in conjunction with spectroscopic ellipsometry. A weak ferromagnetic order, induced alternately by magnetization in the growth direction or by tetragonality, created a magnon oscillation at 75 GHz, indicative of a Dzyaloshinskii-Moriya interaction energy of 0.31 meV.
    Keywords: ATK, Application, experimental comparison
    Area: materials
    BibTeX:
    @article{Doig2013,
      author = {Doig, K. I. and Aguesse, F. and Axelsson, A. K. and Alford, N. M. and Nawaz, S. and Palkar, V. R. and Jones, S. P. P. and Johnson, R. D. and Synowicki, R. A. and Lloyd-Hughes, J.},
      title = {Coherent magnon and acoustic phonon dynamics in tetragonal and rare-earth-doped BiFeO3 multiferroic thin films},
      journal = {Physical Review B},
      publisher = {American Physical Society},
      year = {2013},
      volume = {88},
      number = {9},
      pages = {094425},
      doi = {http://dx.doi.org/10.1103/PhysRevB.88.094425}
    }
    
    Wu Qiu-Hua, Zhao Peng & Liu De-Sheng Low Bias Negative Differential Resistance Behavior in Carbon/Boron Nitride Nanotube Heterostructures 2013 Chinese Physics Letters
    Vol. 30(10), 107304- 
    DOI  
    Abstract: Based on the non-equilibrium Green's method and density functional theory, we investigate the electronic transport properties of ternary heterostructures based on carbon nanotubes and boron nitride nanotubes, with different atomic compositions, coupled to gold electrodes. Negative differential resistance (NDR) behavior can be observed due to suppression of the conduction channel at a certain bias. More importantly, the position of NDR can be tuned into the bias range as low as tens of meV by increasing the length of boron nitride nanotube. The peak-to-valley ratio, which is a typical character of NDR behavior, is also sensitive to the atomic compositions.
    Keywords: ATK, Application, carbon nanotube, boron-nitride, heterostructure, negative differential resistance (NDR)
    Area: nanotubes
    BibTeX:
    @article{Qiu-Hua2013,
      author = {Qiu-Hua, Wu and Peng, Zhao and De-Sheng, Liu},
      title = {Low Bias Negative Differential Resistance Behavior in Carbon/Boron Nitride Nanotube Heterostructures},
      journal = {Chinese Physics Letters},
      year = {2013},
      volume = {30},
      number = {10},
      pages = {107304--},
      doi = {http://dx.doi.org/10.1088/0256-307X/30/10/107304}
    }
    
    Yuta Tsuji, Junya Koga & Kazunari Yoshizawa Asymmetric Diarylethene as a Dual-Functional Device Combining Switch and Diode: 2013 Bulletin of the Chemical Society of Japan
    Vol. 86(8), 947-954 
    DOI  
    Abstract: Diarylethenes are photosensitive pi-conjugated molecules, being of great promise in potential applications to various molecular devices. Although the switching properties of diarylethenes have been widely investigated experimentally and theoretically, little is known about their rectifying diode-like behavior. In this study, electron-transport properties of asymmetric diarylethenes incorporating two different heterocyclic five-membered rings with opposite electronic demands are investigated with the nonequilibrium Green function combined with density functional theory. The aim of this study is to derive the effect of the heteroatomic defects on not only switching but also rectifying characteristics of the asymmetric diarylethenes. Obtained results show that a silicon atom involved in the diarylethenes plays an important role in the current rectifying as well as switching performance. It is found that maximum rectification ratios of the asymmetric diarylethenes increase linearly with an increase in electronegativity difference between the asymmetrically arranged heteroatoms. The silicon- and oxygen-containing asymmetric diarylethene is suggested to be a good potential candidate for a novel molecular electronic device combining a switch and a diode.
    Keywords: ATK, Application, molecular electronics, rectification, defect
    Area: molecular electronics
    BibTeX:
    @article{Tsuji2013a,
      author = {Tsuji, Yuta and Koga, Junya and Yoshizawa, Kazunari},
      title = {Asymmetric Diarylethene as a Dual-Functional Device Combining Switch and Diode: },
      journal = {Bulletin of the Chemical Society of Japan},
      year = {2013},
      volume = {86},
      number = {8},
      pages = {947--954},
      doi = {http://dx.doi.org/10.1246/bcsj.20130089}
    }
    
    J.C. Dong, H. Li, F.W. Sun, K. Zhang & Y.F. Li Theoretical Study of the Properties of Si Nanowire Electronic Devices 2011 J. Phys. Chem. C
    Vol. 115(28)The Journal of Physical Chemistry C, 13901-13906 
    DOI  
    Abstract: Electron-transport properties of three terminal field-effect devices based on both pure and doped Si nanowires with diameters less than 1 nm are theoretically studied. The results indicate that some devices possess electronic functions, such as current amplification and robust negative differential resistance accompanied with large on-off ratios. Three kinds of mechanisms are proposed to interpret different negative differential resistance phenomena of some devices investigated in this paper. Not only structures of nanowires but also applied bias can change the mechanism of negative differential resistance. Furthermore, the performance of these devices is mainly dependent on the doping and atomic arrangement of Si nanowires. This work provides a deep insight into the electron-transport properties of functional electronic nanodevices.
    Keywords: ATK, Application, nanowire, field-effect transistor, doping
    Area: nanowires
    BibTeX:
    @article{Dong2011,
      author = {Dong, J. C. and Li, H. and Sun, F. W. and Zhang, K. and Li, Y. F.},
      title = {Theoretical Study of the Properties of Si Nanowire Electronic Devices},
      booktitle = {The Journal of Physical Chemistry C},
      journal = {J. Phys. Chem. C},
      publisher = {American Chemical Society},
      year = {2011},
      volume = {115},
      number = {28},
      pages = {13901--13906},
      doi = {http://dx.doi.org/10.1021/jp2007045}
    }
    
    Satoshi Kaneko, Jinjiang Zhang, Jianwei Zhao & Manabu Kiguchi Electronic Conductance of Platinum Atomic Contact in a Nitrogen Atmosphere 2013 J. Phys. Chem. C
    Vol. 117(19)The Journal of Physical Chemistry C, 9903-9907 
    DOI  
    Abstract: We have investigated the platinum atomic contact in a nitrogen atmosphere using mechanically controllable break junction technique and theoretical calculation. Conductance, dI/dV measurement, and theoretical calculation revealed a single N2 molecule placed between platinum electrodes, where the N2 molecular axis was parallel to the junction axis. The conductance of the single N2 molecular junction was 1 G0 (=2e2/h), which was comparable to that of metal atomic contacts indicating the strong interaction between the nitrogen molecule and Pt electrodes. Theoretical calculation supported the high conductivity of the molecular junction and revealed that two dominant channels contributed to the electron transport through the junction. The two dominant channels were from the coupling between orbitals (dxz and dyz) of Pt atom and orbitals (px and py) of N atom.
    Keywords: ATK, Application, atomic contact, molecular electronics, break junction
    Area: molecular electronics
    BibTeX:
    @article{Kaneko2013,
      author = {Kaneko, Satoshi and Zhang, Jinjiang and Zhao, Jianwei and Kiguchi, Manabu},
      title = {Electronic Conductance of Platinum Atomic Contact in a Nitrogen Atmosphere},
      booktitle = {The Journal of Physical Chemistry C},
      journal = {J. Phys. Chem. C},
      publisher = {American Chemical Society},
      year = {2013},
      volume = {117},
      number = {19},
      pages = {9903--9907},
      doi = {http://dx.doi.org/10.1021/jp401562d}
    }
    
    Muhammed Ihab Schukfeh, Kristian Storm, Ahmed Mahmoud, Roar R. Søndergaard, Anna Szwajca, Allan Hansen, Peter Hinze, Thomas Weimann, Sofia Fahlvik Svensson, Achyut Bora, Kimberly A. Dick, Claes Thelander, Frederik C. Krebs, Paolo Lugli, Lars Samuelson & Marc Tornow Conductance Enhancement of InAs/InP Heterostructure Nanowires by Surface Functionalization with Oligo(phenylene vinylene)s 2013 ACS Nano
    Vol. 7(5)ACS Nano, 4111-4118 
    DOI  
    Abstract: We have investigated the electronic transport through 3 micrometer long, 45 nm diameter InAs nanowires comprising a 5 nm long InP segment as electronic barrier. After assembly of 12 nm long oligo(phenylene vinylene) derivative molecules onto these InAs/InP nanowires, we observed a pronounced, nonlinear I-V characteristic with significantly increased currents of up to 1 microA at 1 V bias, for a back-gate voltage of 3 V. As supported by our model calculations based on a nonequilibrium Green Function approach, we attribute this effect to charge transport through those surface-bound molecules, which electrically bridge both InAs regions across the embedded InP barrier.
    Keywords: ATK; Application; molecular electronics; nanowire; experimental comparison
    Area: molecular electronics; nanowires
    BibTeX:
    @article{Schukfeh2013,
      author = {Schukfeh, Muhammed Ihab and Storm, Kristian and Mahmoud, Ahmed and Søndergaard, Roar R. and Szwajca, Anna and Hansen, Allan and Hinze, Peter and Weimann, Thomas and Svensson, Sofia Fahlvik and Bora, Achyut and Dick, Kimberly A. and Thelander, Claes and Krebs, Frederik C. and Lugli, Paolo and Samuelson, Lars and Tornow, Marc},
      title = {Conductance Enhancement of InAs/InP Heterostructure Nanowires by Surface Functionalization with Oligo(phenylene vinylene)s},
      booktitle = {ACS Nano},
      journal = {ACS Nano},
      publisher = {American Chemical Society},
      year = {2013},
      volume = {7},
      number = {5},
      pages = {4111--4118},
      doi = {http://dx.doi.org/10.1021/nn400380g}
    }
    
    Xi-Feng Shi, Na Li, Ke Zhao, Guan-Wei Cui, Ying-Qiang Zhao, Ming-Yue Ma, Ke-Hua Xu, Ping Li, Yu-Bin Dong & Bo Tang A dye-sensitized FeOOH-CNT photocatalyst with three electron transfer channels regulated by hydrogen bonding 2013 Applied Catalysis B: Environmental
    Vol. 136-137(0), 334-340 
    DOI  
    Abstract: A dye-sensitized photocatalyst with three electron transfer channels was constructed, in which FeOOH and photosensitizer RuL2Cl2·2H2O were employed as the electron donor, carbon nanotubes were served as the electron container. The catalytic activities of the photocatalyst were evaluated by a model photocatalytic carboxylation reaction of phenol by CO2. The photocatalytic efficiency and transient photocurrent density increased obviously when the catalysis reaction was carried out in cyclohexane compared to two electron activations in water, which suggested the formation of three electron transfer channels in the catalytic system. Moreover, time-dependent density functional theory (TD-DFT) calculation results also indicated the existence of three electron transfer channels assisted by intermolecular hydrogen bonding interaction.
    Keywords: ATK, Application, photocatalysis, electron transfer, three channels, hydrogen bonding, nanotube
    Area: nanotubes
    BibTeX:
    @article{Shi2013,
      author = {Shi, Xi-Feng and Li, Na and Zhao, Ke and Cui, Guan-Wei and Zhao, Ying-Qiang and Ma, Ming-Yue and Xu, Ke-Hua and Li, Ping and Dong, Yu-Bin and Tang, Bo},
      title = {A dye-sensitized FeOOH-CNT photocatalyst with three electron transfer channels regulated by hydrogen bonding},
      journal = {Applied Catalysis B: Environmental},
      year = {2013},
      volume = {136-137},
      number = {0},
      pages = {334--340},
      doi = {http://dx.doi.org/10.1016/j.apcatb.2013.02.005}
    }
    
    Yuta Tsuji & Kazunari Yoshizawa Current Rectification through pi-pi Stacking in Multilayered Donor-Acceptor Cyclophanes 2012 J. Phys. Chem. C
    Vol. 116(50)The Journal of Physical Chemistry C, 26625-26635 
    DOI  
    Abstract: Extended pi-stacked molecules have attracted much attention since they play an essential role in both electronic devices and biological systems. In this article electron transport properties of a series of multilayered cyclophanes with the hydroquinone donor and quinone acceptor units in the external positions are theoretically studied with applications to molecular rectifiers in mind. Calculations of electron transport through the pi-pi stacked structures in the multilayered cyclophanes are performed by using nonequilibrium Green's function method combined with density functional theory. Calculated transmission spectra show that the conductance decreases exponentially with the length of the molecule with a decay factor of 0.75 Å^-1, which lies for the values between pi-conjugated molecules and sigma-bonded molecules. Applied bias calculations provide current-voltage curves, which exhibit good rectifying behavior. The rectification mechanism in the coherent transport regime is qualitatively explained by the response of the frontier orbital energy levels, especially LUMO levels, to the applied bias, where the rectifying direction is expected to be opposite to the Aviram-Ratner model. The maximum value of rectification ratio increases with an increase in the number of stacking layers due to the effective separation of the donor and acceptor parts, where effects from the opposite electrodes to the donor and acceptor are negligible. Multilayered donor-acceptor cyclophanes are suitable materials for investigating the relationship among electron transport properties, rectification properties, and molecular length (separation between the donor and acceptor parts).
    Keywords: ATK; Application; molecular electronics; rectification
    Area: molecular electronics
    BibTeX:
    @article{Tsuji2012b,
      author = {Tsuji, Yuta and Yoshizawa, Kazunari},
      title = {Current Rectification through pi-pi Stacking in Multilayered Donor-Acceptor Cyclophanes},
      booktitle = {The Journal of Physical Chemistry C},
      journal = {J. Phys. Chem. C},
      publisher = {American Chemical Society},
      year = {2012},
      volume = {116},
      number = {50},
      pages = {26625--26635},
      doi = {http://dx.doi.org/10.1021/jp308849t}
    }
    
    Y. Min, J.H. Fang, C.G. Zhong, Z.C. Dong, C.P. Chen & K.L. Yao Localization of the energy states of lead inducing the effect of rectification and negative differential resistance predicted by first-principles study 2013 Int. J. Mod. Phys. B
    Vol. 27(17)International Journal of Modern Physics B, 1350081 
    DOI  
    Abstract: The first-principles calculations of the transport characteristics of 4-(5-(2-(5-(4-mercaptophenyl)thiophene-2-yl)ethyl)pyridin-2-yl)benzenethiol sandwiched between two gold leads are performed. The effect of rectification and negative differential resistance (NDR) are obtained, which promise the potential applications in the field of molecular electronics. The rectification effect is 4.49. The peak/valley ratio of the NDR effect is as large as 4.51 for the forward bias and 12.09 for the reverse bias. The strong coupling between gold lead and molecule through thiolate results in the localization of the energy states of gold lead, which may induce the effect of rectification and NDR.
    Keywords: ATK; Application; molecular electronics; density functional theory; nonequilibrium Green's function; electrons transport; LDOS
    Area: molecular electronics
    BibTeX:
    @article{Min2013a,
      author = {Min, Y. and Fang, J. H. and Zhong, C. G. and Dong, Z. C. and Chen, C. P. and Yao, K. L.},
      title = {Localization of the energy states of lead inducing the effect of rectification and negative differential resistance predicted by first-principles study},
      booktitle = {International Journal of Modern Physics B},
      journal = {Int. J. Mod. Phys. B},
      publisher = {World Scientific Publishing Co.},
      year = {2013},
      volume = {27},
      number = {17},
      pages = {1350081},
      doi = {http://dx.doi.org/10.1142/S0217979213500811}
    }
    
    Bin Cui, Yuqing Xu, Guomin Ji, Hui Wang, Wenkai Zhao, Yaxin Zhai, Dongmei Li & Desheng Liu A single-molecule diode with significant rectification and negative differential resistance behavior 2014 Organic Electronics
    Vol. 15(2), 484-490 
    DOI  
    Abstract: A series of ferrocenylalkanethiol (HSCnFc) single molecular junctions are modeled and their rectification ratios (RRs) are up to 100 (for HSC11Fc), which agrees with the experiments of Whitesides et al. Not only explanation to the origin of the remarkable large RR is given, but also the reason why one order deviation of RR between HSC11Fc and HSC9Fc is discussed and depicted, which was not pointed out by previous researchers. The single asymmetric accessible molecular orbital (MO) model is evaluated, which is different from the Donor (D)-Acceptor (A) models reported before and a clear negative differential resistance (NDR) behavior is found and explained in the HSC11Fc based device.
    Keywords: ATK, Application, non-equilibrium Green's function, unimolecular diode, gate modulation, rectification, experimental comparison, doping
    Area: molecular electronics
    BibTeX:
    @article{Cui2014b,
      author = {Cui, Bin and Xu, Yuqing and Ji, Guomin and Wang, Hui and Zhao, Wenkai and Zhai, Yaxin and Li, Dongmei and Liu, Desheng},
      title = {A single-molecule diode with significant rectification and negative differential resistance behavior},
      journal = {Organic Electronics},
      year = {2014},
      volume = {15},
      number = {2},
      pages = {484--490},
      doi = {http://dx.doi.org/10.1016/j.orgel.2013.11.039}
    }
    
    Milanpreet Kaur, Ravinder Singh Sawhney & Harsimran Kaur Anatomizing electronic transport through saturated alkane molecule with disparate terminal elements 2012 J. Multiscale Modelling
    Vol. 044(03)Journal of Multiscale Modelling, 1250011 
    DOI  
    Abstract: In this paper, we anatomized transport properties of butane belonging to the saturated alkane group (CnH2n+2) using three terminal anchor elements (nitrogen, oxygen and sulfur) in Trans configuration connected to gold electrodes, forming a two probe model. The transport properties of three variants of butane were investigated in terms of Transmission spectra, Eigenstates, I-V characteristics and differential conductance for different values of biasing voltage using Keldysh's non-equilibrium Green's function combined with semi-empirical extended Hückel theory. Amongst the three binding elements, Butane exhibited maximum charge transfer with sulfur, then with nitrogen and least with oxygen. The HOMO-LUMO gap for both nitrogen and Oxygen as terminal anchoring elements suggested that conduction was virtually impossible through Butane in particular cases. Nature of Ballistic current for butane anchored with sulfur is ideal for its applicability as nano-diode or resonant tunneling diodes (RTDs) in arena of quantum-electronics due to its strong coupling between the terminal atoms and carbon atoms of butane. The retrenching order obtained in terms of conductance is S > N > O anchored butane molecule which seemed in full confirmation with the results of Transmission spectrum and its Eigenstates and proved sulfur to be a promising binding element and can produce much better results in comparison to oxygen and nitrogen. This paper marked another step in the field of molecular electronics as the butane anchored with sulfur has characteristics in conjunction to the semiconductor junction diode.
    Keywords: ATK; Application; molecular electronics; extended Hückel theory (EHT); non-equilibrium Green's function (NEGF); butane (C4H10); highest occupied molecular orbital (HOMO); Lowest unoccupied molecular orbital (LUMO)
    Area: molecular electronics
    BibTeX:
    @article{Kaur2012,
      author = {Kaur, Milanpreet and Sawhney, Ravinder Singh and Kaur, Harsimran},
      title = {Anatomizing electronic transport through saturated alkane molecule with disparate terminal elements},
      booktitle = {Journal of Multiscale Modelling},
      journal = {J. Multiscale Modelling},
      publisher = {World Scientific Publishing Co.},
      year = {2012},
      volume = {044},
      number = {03},
      pages = {1250011},
      doi = {http://dx.doi.org/10.1142/S1756973712500114}
    }
    
    H.J. Liu Thermoelectric Properties of Carbon Nanotubes and Related One-Dimensional Structures 2014
    Vol. 16Lecture Notes in Nanoscale Science and Technology, 363-391 
    DOI  
    Abstract: Using nonequilibrium molecular dynamics simulations and nonequilibrium Green's function method, we investigate the thermoelectric properties of carbon nanotubes and related one-dimensional structures, which include ultrasmall and larger diameter carbon nanotubes, as well as graphene nanoribbons (GNRs) and carbon nanowires (CNWs). It is found that the transmission function of these one-dimensional carbon nanostructures display a clear stepwise structure that gives the number of electron channels. By optimizing the carrier concentration, characteristic size, and/or operating temperature, these systems could exhibit very high figure of merit. Moreover, their thermoelectric performance can be significantly enhanced via man approaches such as surface design, isotope substitution, isoelectronic impurities, and hydrogen adsorption. It is thus reasonable to expect that carbon nanotubes and related one-dimensional carbon nanostructures may be promising candidates for high-performance thermoelectric materials.
    Keywords: ATK, Application, thermoelectric properties, molecular dynamics, graphene, nanotubes
    Area: graphene; nanotubes; thermo
    BibTeX:
    @incollection{Liu2014,
      author = {Liu, H.J.},
      title = {Thermoelectric Properties of Carbon Nanotubes and Related One-Dimensional Structures},
      booktitle = {Lecture Notes in Nanoscale Science and Technology},
      publisher = {Springer International Publishing},
      year = {2014},
      volume = {16},
      pages = {363-391},
      doi = {http://dx.doi.org/10.1007/978-3-319-02012-9_12}
    }
    
    Li Ming-Jun, Long Meng-Qiu & Xu Hui Effects of the Bridging Bond on Electronic Transport in a D-B-A Device 2013 Chinese Physics Letters
    Vol. 30(8), 087201- 
    DOI  
    Abstract: By using density functional theory combined with a nonequilibrium Green's functions approach, the electronic transport properties of different bridges connecting benzene-based heterojunction molecular devices are investigated. We focus on the effects of the bridging bond polarity and its bond length. Our results show that the polar bond plays a significant role in determining the overall conductance of the molecular devices. The effects of a current plateau and the negative differential resistance can be observed. These simulation results suggest that the proposed models may be helpful for designing practical molecular devices.
    Keywords: ATK, Application, molecular electronics
    Area: molecular electronics
    BibTeX:
    @article{Ming-Jun2013,
      author = {Ming-Jun, Li and Meng-Qiu, Long and Hui, Xu},
      title = {Effects of the Bridging Bond on Electronic Transport in a D-B-A Device},
      journal = {Chinese Physics Letters},
      year = {2013},
      volume = {30},
      number = {8},
      pages = {087201--},
      doi = {http://dx.doi.org/10.1088/0256-307X/30/8/087201}
    }
    
    R Quhe, J Ma, Z Zeng, K Tang, J Zheng, Y Wang, Z Ni, L Wang, Z Gao, J Shi & J Lu Tunable band gap in few-layer graphene by surface adsorption. 2013 Sci Rep
    Vol. 3, 1794 
    DOI  
    Abstract: There is a tunable band gap in ABC-stacked few-layer graphene (FLG) via applying a vertical electric field, but the operation of FLG-based field effect transistor (FET) requires two gates to create a band gap and tune channel's conductance individually. Using first principle calculations, we propose an alternative scheme to open a band gap in ABC-stacked FLG namely via single-side adsorption. The band gap is generally proportional to the charge transfer density. The capability to open a band gap of metal adsorption decreases in this order: K/Al > Cu/Ag/Au > Pt. Moreover, we find that even the band gap of ABA-stacked FLG can be opened if the bond symmetry is broken. Finally, a single-gated FET based on Cu-adsorbed ABC-stacked trilayer graphene is simulated. A clear transmission gap is observed, which is comparable with the band gap. This renders metal-adsorbed FLG a promising channel in a single-gated FET device.
    Keywords: ATK; Application; graphene; few-layer graphene; field-effect transistor
    Area: graphene
    BibTeX:
    @article{Quhe2013,
      author = {Quhe, R and Ma, J and Zeng, Z and Tang, K and Zheng, J and Wang, Y and Ni, Z and Wang, L and Gao, Z and Shi, J and Lu, J},
      title = {Tunable band gap in few-layer graphene by surface adsorption.},
      journal = {Sci Rep},
      year = {2013},
      volume = {3},
      pages = {1794},
      doi = {http://dx.doi.org/10.1038/srep01794}
    }
    
    Kamal K. Saha & Branislav K. Nikolic Negative differential resistance in graphene-nanoribbon-carbon-nanotube crossbars: a first-principles multiterminal quantum transport study 2013 Journal of Computational Electronics
    Vol. 12(4)Journal of Computational Electronics, 542-552 
    DOI  
    Abstract: We simulate quantum transport between a graphene nanoribbon (GNR) and a single-walled carbon nanotube (CNT) where electrons traverse vacuum gap between them. The GNR covers CNT over a nanoscale region while their relative rotation is 90 degrees, thereby forming a four-terminal crossbar where the bias voltage is applied between CNT and GNR terminals. The CNT and GNR are chosen as either semiconducting (s) or metallic (m) based on whether their two-terminal conductance exhibits a gap as a function of the Fermi energy or not, respectively. We find nonlinear current-voltage (I-V) characteristics in all three investigated devices - mGNR-sCNT, sGNR-sCNT and mGNR-mCNT crossbars - which are asymmetric with respect to changing the bias voltage from positive to negative. Furthermore, the I-V characteristics of mGNR-sCNT crossbar exhibits negative differential resistance (NDR) with low onset voltage V NDR ~0.25 V and peak-to-valley current ratio ~2.0. The overlap region of the crossbars contains only ~460 carbon and hydrogen atoms which paves the way for nanoelectronic devices ultrascaled well below the smallest horizontal length scale envisioned by the international technology roadmap for semiconductors. Our analysis is based on the nonequilibrium Green function formalism combined with density functional theory (NEGF-DFT), where we also provide an overview of recent extensions of NEGF-DFT framework (originally developed for two-terminal devices) to multiterminal devices.
    Keywords: ATK, Application, Crossed nanowires, negative differential resistance, NDR, graphene nanoribbons, carbon nanotubes, multiterminal nanostructures, first-principles quantum transport
    Area: graphene; nanotubes
    BibTeX:
    @article{Saha2013,
      author = {Saha, Kamal K. and Nikolic, Branislav K.},
      title = {Negative differential resistance in graphene-nanoribbon-carbon-nanotube crossbars: a first-principles multiterminal quantum transport study},
      booktitle = {Journal of Computational Electronics},
      journal = {Journal of Computational Electronics},
      publisher = {Springer US},
      year = {2013},
      volume = {12},
      number = {4},
      pages = {542-552},
      doi = {http://dx.doi.org/10.1007/s10825-013-0534-z}
    }
    
    Sabyasachi Sen & Swapan Chakrabarti In silico design of a tunable molecular spin filter using chromium-carbon-chromium chains 2014 Chemical Physics
    Vol. 428(0), 34-42 
    DOI  
    Abstract: We report on the potential use of Cr-C_n-Cr as a tunable molecular spin filter. Our study reveals that by suitably engineering the number of carbon atoms between the two Cr atoms, very strong spin filter efficiency could be achieved. An even-odd oscillation has been observed both in the spin polarized conductance as well as spin filter efficiency and it is reported that only with even number of carbon atoms the spin filter efficiency of the systems become 99.99%. Results obtained from the state-of-the-art nonequilibrium Green's function based calculations has been validated by analyzing the spin polarized transmission spectra, density of states, and molecular projected self consistent Hamiltonian states obtained at specific length of the carbon chain. The modification in singly occupied highest molecular orbital on going from odd to even number of carbon atoms explains the origin of the even-odd oscillation.
    Keywords: ATK, Application, transition metal-carbon cluster, tunable molecular spin filter, spin filter efficiency, even-odd oscillation
    Area: molecular electronics; spin
    BibTeX:
    @article{Sen2014,
      author = {Sen, Sabyasachi and Chakrabarti, Swapan},
      title = {In silico design of a tunable molecular spin filter using chromium-carbon-chromium chains},
      journal = {Chemical Physics},
      year = {2014},
      volume = {428},
      number = {0},
      pages = {34--42},
      doi = {http://dx.doi.org/10.1016/j.chemphys.2013.10.022}
    }
    
    Amretashis Sengupta & Santanu Mahapatra Negative differential resistance and effect of defects and deformations in MoS2 armchair nanoribbon metal-oxide-semiconductor field effect transistor 2013 Journal of Applied Physics
    Vol. 114(19), - 
    DOI  
    Abstract: In this work, we present a study on the negative differential resistance (NDR) behavior and the impact of various deformations (like ripple, twist, wrap) and defects like vacancies and edge roughness on the electronic properties of short-channel MoS2 armchair nanoribbon MOSFETs. The effect of deformation (3-7 degree twist or wrap and 0.3-0.7 Å ripple amplitude) and defects on a 10 nm MoS2 ANR FET is evaluated by the density functional tight binding theory and the non-equilibrium Green's function approach. We study the channel density of states, transmission spectra, and the ID-VD characteristics of such devices under the varying conditions, with focus on the NDR behavior. Our results show significant change in the NDR peak to valley ratio and the NDR window with such minor intrinsic deformations, especially with the ripple.
    Keywords: ATK, Application, MoS2 nanoribbon, molybdenum compounds, negative differential resistance (NDR), deformation, field-effect transistor (FET)
    Area: 2dmat, tmd
    BibTeX:
    @article{Sengupta2013b,
      author = {Sengupta, Amretashis and Mahapatra, Santanu},
      title = {Negative differential resistance and effect of defects and deformations in MoS2 armchair nanoribbon metal-oxide-semiconductor field effect transistor},
      journal = {Journal of Applied Physics},
      year = {2013},
      volume = {114},
      number = {19},
      pages = {-},
      doi = {http://dx.doi.org/10.1063/1.4833554}
    }
    
    Daniel Valencia, Jun-Qiang Lu, Jian Wu, Feng Liu, Feng Zhai & Yong-Jin Jiang Electronic transmission in graphene suppressed by interlayer interference 2013 AIP Advances
    Vol. 3(10), 102125 
    DOI  
    Abstract: We investigate electronic transport property of a graphene monolayer covered by a graphene nanoribbon. We demonstrate that electronic transmission of a monolayer can be reduced when covered by a nanoribbon. The energy at which the transmission reduction occurs depends on the width of nanoribbon. We explain the transmission reduction as interference between wavefunctions in the monolayer and the nanoribbon. Furthermore, we show that the transmission reduction of a monolayer is combinable when covered by more than one nanoribbon and we propose a concept of "combination of control" for possible nano-application designs.
    Keywords: ATK, Application, wave functions, graphene nanoribbon
    Area: graphene
    BibTeX:
    @article{Valencia2013,
      author = {Valencia, Daniel and Lu, Jun-Qiang and Wu, Jian and Liu, Feng and Zhai, Feng and Jiang, Yong-Jin},
      title = {Electronic transmission in graphene suppressed by interlayer interference},
      journal = {AIP Advances},
      year = {2013},
      volume = {3},
      number = {10},
      pages = {102125},
      doi = {http://dx.doi.org/10.1063/1.4827022}
    }
    
    Le-Jia Wang, Ai Yong, Kai-Ge Zhou, Lin Tan, Jian Ye, Guo-Ping Wu, Zhu-Guo Xu & Hao-Li Zhang Conformation-Controlled Electron Transport in Single-Molecule Junctions Containing Oligo(phenylene ethynylene) Derivatives 2013 Chem. Asian J.
    Vol. 8(8), 1901-1909 
    DOI  
    Abstract: Understanding the relationships between the molecular structure and electronic transport characteristics of single-molecule junctions is of fundamental and technological importance for future molecular electronics. Herein, we report a combined experimental and theoretical study on the single-molecule conductance of a series of oligo(phenylene ethynylene) (OPE) molecular wires, which consist of two phenyl-ethynyl-phenyl pi units with different dihedral angles. The molecular conductance was studied by scanning tunneling microscopy (STM)-based break-junction techniques under different conditions, including variable temperature and bias potential, which suggested that a coherent tunneling mechanism takes place in the OPE molecular wires with a length of 2.5 nm. The conductance of OPE molecular junctions are strongly affected by the coupling strength between the two pi systems, which can be tuned by controlling their intramolecular conformation. A cos(2theta) dependence was revealed between the molecular conductance and dihedral angles between the two conjugated units. Theoretical investigations on the basis of density functional theory and nonequilibrium Green's functions (NEGF) gave consistent results with the experimental observations and provided insights into the conformation-dominated molecular conductance.
    Keywords: ATK; Application; conducting materials; conformation analysis; electron transport; molecular electronics; single-molecule studies; experimental comparison; charge-transport; quantized conductance; orbital energies; dependence; contacts; conductivity; temperature; fabrication; transition; rectifiers
    Area: molecular electronics
    BibTeX:
    @article{Wang2013c,
      author = {Wang, Le-Jia and Yong, Ai and Zhou, Kai-Ge and Tan, Lin and Ye, Jian and Wu, Guo-Ping and Xu, Zhu-Guo and Zhang, Hao-Li},
      title = {Conformation-Controlled Electron Transport in Single-Molecule Junctions Containing Oligo(phenylene ethynylene) Derivatives},
      journal = {Chem. Asian J.},
      publisher = {WILEY-VCH Verlag},
      year = {2013},
      volume = {8},
      number = {8},
      pages = {1901--1909},
      doi = {http://dx.doi.org/10.1002/asia.201300264}
    }
    
    Z. Yang, B.L. Zhang, X.G. Liu, Y.Z. Yang, X.Y. Li, S.J. Xiong & B.S. Xu Spin-valve giant magnetoresistance in scandium-benzene sandwich cluster 2013 EPL (Europhysics Letters)
    Vol. 104(5), 50006- 
    DOI  
    Abstract: Using density functional theory and non-equilibrium Green's function method, we investigate the magnetic and transport properties of organic Sc n (C 6 H 6 ) n +1 (n=1-3) sandwich clusters. The results show that the sandwiches possess high stabilities and large magnetic moments, and our prediction is in agreement with the experimental observation. With Ni as two electrodes, significant spin-valve giant magnetoresistance was found in Sc 3 (C 6 H 6 ) 4 molecular junction. Furthermore, all the sandwiches can be viewed as a new kind of spin filter. Specially, by changing the magnetization orientation of one electrode, Sc 2 (C 6 H 6 ) 3 molecular junction could effectively control the spin orientation of the electron in the system.
    Keywords: ATK, Application, sandwich cluster, spin, experimental comparison, magnetism, single-electron transistor, complexes
    Area: molecular electronics; spin
    BibTeX:
    @article{Yang2013c,
      author = {Yang, Z. and Zhang, B. L. and Liu, X. G. and Yang, Y. Z. and Li, X. Y. and Xiong, S. J. and Xu, B. S.},
      title = {Spin-valve giant magnetoresistance in scandium-benzene sandwich cluster},
      journal = {EPL (Europhysics Letters)},
      year = {2013},
      volume = {104},
      number = {5},
      pages = {50006--},
      doi = {http://dx.doi.org/10.1209/0295-5075/104/50006}
    }
    
    Wen Yang, Lu-Hao Wang, Yang Geng, Qing-Qing Sun, Peng Zhou, Shi-Jing Ding & David Wei Zhang Atomic scale investigations of the gate controlled tunneling effect in graphyne nanoribbon 2013 Journal of Applied Physics
    Vol. 114(22), 224311 
    DOI  
    Abstract: Configuration and transport properties of zigzag graphyne nanoribbon (n=2) are investigated by means of the first-principles calculations and non-equilibrium Green's function in this work. We demonstrated the controllability of the graphyne's conductivity by gate bias, and the tunneling behavior induced by gate and drain voltages was investigated systemically. The characteristics of Id-Vd, Id-Vg, as well as the evolutions of current with electron temperature elevation were explored. The device exhibits a tunneling ratio around 10^3, and the state art of tunneling operations of the tunneling field effect transistor in this split-new material was achieved.
    Keywords: ATK; Application; electrical conductivity; graphyne nanoribbon; tunneling field-effect transistor (TFET)
    Area: graphene
    BibTeX:
    @article{Yang2013d,
      author = {Yang, Wen and Wang, Lu-Hao and Geng, Yang and Sun, Qing-Qing and Zhou, Peng and Ding, Shi-Jing and Wei Zhang, David},
      title = {Atomic scale investigations of the gate controlled tunneling effect in graphyne nanoribbon},
      journal = {Journal of Applied Physics},
      year = {2013},
      volume = {114},
      number = {22},
      pages = {224311},
      doi = {http://dx.doi.org/10.1063/1.4836876}
    }
    
    Jiaxin Zheng, Yangyang Wang, Lu Wang, Ruge Quhe, Zeyuan Ni, Wai-Ning Mei, Zhengxiang Gao, Dapeng Yu, Junjie Shi & Jing Lu Interfacial Properties of Bilayer and Trilayer Graphene on Metal Substrates 2013 Sci. Rep.
    Vol. 3, 2081 
    DOI  
    Abstract: One popular approach to prepare graphene is to grow them on transition metal substrates via chemical vapor deposition. By using the density functional theory with dispersion correction, we systematically investigate for the first time the interfacial properties of bilayer (BLG) and trilayer graphene (TLG) on metal substrates. Three categories of interfacial structures are revealed. The adsorption of B(T)LG on Al, Ag, Cu, Au, and Pt substrates is a weak physisorption, but a band gap can be opened. The adsorption of B(T)LG on Ti, Ni, and Co substrates is a strong chemisorption, and a stacking-insensitive band gap is opened for the two uncontacted layers of TLG. The adsorption of B(T)LG on Pd substrate is a weaker chemisorption, with a band gap opened for the uncontacted layers. This fundamental study also helps for B(T)LG device study due to inevitable graphene/metal contact.
    Keywords: ATK; Application; graphene;
    Area: graphene
    BibTeX:
    @article{Zheng2013b,
      author = {Zheng, Jiaxin and Wang, Yangyang and Wang, Lu and Quhe, Ruge and Ni, Zeyuan and Mei, Wai-Ning and Gao, Zhengxiang and Yu, Dapeng and Shi, Junjie and Lu, Jing},
      title = {Interfacial Properties of Bilayer and Trilayer Graphene on Metal Substrates},
      journal = {Sci. Rep.},
      publisher = {Macmillan Publishers Limited. All rights reserved},
      year = {2013},
      volume = {3},
      pages = {2081},
      doi = {http://dx.doi.org/10.1038/srep02081}
    }
    
    R. Zhou, L.C. Lew Yan Voon & Y. Zhuang Properties of two-dimensional silicon grown on graphene substrate 2013 Journal of Applied Physics
    Vol. 114(9), 093711 
    DOI  
    Abstract: The structure and electrical properties of two-dimensional (2D) sheets of silicon on a graphene substrate are studied using first-principles calculations. Two forms of corrugated silicon sheets are proposed to be energetically favorable structures. A shift of the Fermi energy level is found in both corrugated structures. Calculations of electron density show a weak coupling between the silicon layer and graphene substrate in both structures. The two forms of 2D silicon sheets turn out to be metallic and exhibit anisotropic transport properties.
    Keywords: ATK; Application; silicene; graphene; electronic structure
    Area: 2dmat, graphene
    BibTeX:
    @article{Zhou2013a,
      author = {Zhou, R. and Lew Yan Voon, L. C. and Zhuang, Y.},
      title = {Properties of two-dimensional silicon grown on graphene substrate},
      journal = {Journal of Applied Physics},
      year = {2013},
      volume = {114},
      number = {9},
      pages = {093711},
      doi = {http://dx.doi.org/10.1063/1.4820473}
    }
    
    Andreas Zienert, Jörg Schuster, Reinhard Streiter & Thomas Gessner Transport in carbon nanotubes: Contact models and size effects 2010 phys. stat. sol. (b)
    Vol. 247(11-12), 3002-3005 
    DOI  
    Abstract: We present electronic transport calculations for single wall carbon nanotubes (CNTs) using two highly idealized models to describe the electrodes and their contact to the CNT. In the first model we use CNT-electrodes and in the second one we apply the wide-band approximation, neglecting any atomic structure within the electrodes. The single orbital tight-binding approximation is used to describe the electronic structure of the CNTs. This enables us to apply highly efficient decimation techniques to reduce the size of the finite central Hamiltonian. Semi-infinite CNT-electrodes can be included iteratively using a similar method. Electronic transport calculations are carried out within the Landauer formalism.
    Keywords: ATK-SE, Application, carbon nanotubes, electronic transport, Greens function, Landauer formalism
    Area: nanotubes
    BibTeX:
    @article{Zienert2010,
      author = {Zienert, Andreas and Schuster, Jörg and Streiter, Reinhard and Gessner, Thomas},
      title = {Transport in carbon nanotubes: Contact models and size effects},
      journal = {phys. stat. sol. (b)},
      publisher = {WILEY-VCH Verlag},
      year = {2010},
      volume = {247},
      number = {11-12},
      pages = {3002--3005},
      doi = {http://dx.doi.org/10.1002/pssb.201000178}
    }
    
    Andreas Zienert Electronic Transport in Metallic Carbon Nanotubes with Metal Contacts 2013 School: Chemnitz University of Technology  URL 
    Abstract: The continuous migration to smaller feature sizes puts high demands on materials and technologies for future ultra-large-scale integrated circuits. Particularly, the copper-based interconnect system will reach fundamental limits soon. Their outstanding properties make metallic carbon nanotubes (CNTs) an ideal material to partially replace copper in future interconnect architectures. Here, a low contact resistance to existing metal lines is crucial. The present thesis contributes to the theory and numerical description of electronic transport in metallic CNTs with metal contacts. Different theoretical approaches are applied to various contact models and electrode materials (Al, Cu, Pd, Ag, Pt, Au) are compared. Ballistic transport calculations are based on the non-equilibrium Greens function formalism combined with tight-binding (TB), extended Hückel theory (EHT) and density functional theory (DFT). Simplified contact models allow a qualitative investigation of both the influence of geometry and CNT length, and the strength and extent of the contact on the transport properties. In addition, such simple contact models are used to compare the influence of different electronic structure methods on transport. It is found that the semiempirical TB and EHT are inadequate to quantitatively reproduce the DFT-based results. Based on this observation, an improved set of Hückel parameters is developed, which remedies this insufficiency. A systematic investigation of different contact materials is carried out using well defined atomistic metal-CNT-metal structures, optimized in a systematic way. Analytical models for the CNT-metal interaction are proposed. Based on that, electronic transport calculations are carried out, which can be extended to large systems by applying the computationally cheap improved EHT. The metal-CNT-metal systems can then be ranked by average conductance: Ag <= Au < Cu < Pt <= Pd < Al. This corresponds qualitatively with calculated contact distances, binding energies and work functions of CNTs and metals. To gain a deeper understanding of the transport properties, the electronic structure of the metal-CNT-metal systems and their respective parts is analyzed in detail. Here, the energy resolved local density of states is a valuable tool to investigate the CNT-metal interaction and its influences on the transport.
    Keywords: ATK; ATK-SE; Application; metal-nanotube contact; contact resistance; parameter fitting
    Area: nanotubes
    BibTeX:
    @phdthesis{Zienert2013a,
      author = {Andreas Zienert},
      title = {Electronic Transport in Metallic Carbon Nanotubes with Metal Contacts},
      school = {Chemnitz University of Technology},
      year = {2013},
      url = {http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-108205}
    }
    
    Andreas Zienert, Jörg Schuster & Thomas Gessner Comparison of quantum mechanical methods for the simulation of electronic transport through carbon nanotubes 2013 Microelectronic Engineering
    Vol. 106(0), 100-105 
    DOI  
    Abstract: In the present work we study the electronic transport properties of finite length single-wall carbon nanotubes (CNTs) by comparing three different theoretical frameworks. A simple model is used to describe the electrodes and the way they are attached to both ends of the CNT. Electron transport calculations are carried out on three different levels of sophistication. That are the Landauer transport formalism in combination with single-orbital tight-binding, extended Hückel theory or density functional theory. The quantum mechanical transmission which plays a central role in Landauer theory is calculated by means of equilibrium and non-equilibrium Green's function methods. Results of the three approaches are compared and discussed.
    Keywords: ATK, Application, carbon nanotube, electronic transport, Greens's function, tight-binding, extended Hückel theory, density functional theory
    Area: nanotubes
    BibTeX:
    @article{Zienert2013b,
      author = {Zienert, Andreas and Schuster, Jörg and Gessner, Thomas},
      title = {Comparison of quantum mechanical methods for the simulation of electronic transport through carbon nanotubes},
      journal = {Microelectronic Engineering},
      year = {2013},
      volume = {106},
      number = {0},
      pages = {100--105},
      doi = {http://dx.doi.org/10.1016/j.mee.2012.12.018}
    }
    
    S. Barzilai, F. Tavazza & L.E. Levine Disparate effects of an O2 internal impurity on the elongation and quantum transport of gold and silver nanowires 2013 Journal of Applied Physics
    Vol. 114(7), 074315 
    DOI  
    Abstract: In this work, we investigated the effects of an internal O2 impurity on the conductance of elongated gold and silver nanowires (NWs) using density functional theory calculations. We found that the O2 interacts with these metallic NWs very differently. In the case of gold NWs, the presence of an internal oxygen molecule locally strengthens the wire, therefore, forcing the phase transformations connected to the thinning process (3D to 2D and 2D to single atom chain) to occur far from the oxygen. As a consequence, towards the end of the elongation, the internal O2 is located far from the main conductance channel and therefore has little influence on the conductance of the NW. In contrast, in silver NWs, the presence of an internal oxygen molecule involves a larger charge transfer from the metallic atoms to the oxygen, therefore, weakening the Ag-Ag binding. During the initial stages of the elongation, several metallic bonds adjacent to the impurity break, so that in most simulations the NW thinning takes place near the O2. This thinning mechanism places the O2 near the main conductance channel, therefore, significantly reducing the conductivity of the elongated silver NWs. For both metals, our findings agree well with the published experimental results.
    Keywords: ATK-SE, ATK, Application, mechanical properties, electric admittance, nanowires, impurities, geometry optimization; conductance; molecules
    Area: nanowires
    BibTeX:
    @article{Barzilai2013d,
      author = {Barzilai, S. and Tavazza, F. and Levine, L. E.},
      title = {Disparate effects of an O2 internal impurity on the elongation and quantum transport of gold and silver nanowires},
      journal = {Journal of Applied Physics},
      year = {2013},
      volume = {114},
      number = {7},
      pages = {074315},
      doi = {http://dx.doi.org/10.1063/1.4818956}
    }
    
    S Barzilai, F Tavazza & L E Levine Structure stability and electronic transport of gold nanowires on a BeO (001) surface 2013 Modelling and Simulation in Materials Science and Engineering
    Vol. 21(7), 075003 
    DOI  
    Abstract: Gold nanowires (NWs) exhibit remarkable structural and electrical properties, making them good candidates for practical nanoelectronic devices. For such engineering applications, alpha-wurtzite BeO may be a useful platform for supporting these NWs, because gold atoms are attracted to this surface and the atom separation of the BeO (001) surface is compatible with the Au-Au atom spacing. However, the influence of this substrate on the NW conductivity and structure is not known. Here, the stability and conductance of several Au NW configurations on BeO (001) surfaces are investigated using ab initio simulations. It was found that the beryllium-terminated surface preserves the configuration for most of the NWs while the oxygen-terminated surface changes and even repels most of the NW configurations. The electronic structure and the transmission properties of the stable cases showed small changes in the electronic structure of gold NWs due to the presence of the BeO substrate. These changes do not restrict the conduction of the NWs and even enhance it by increasing the capacity of the existing transmission channels, and forming new conduction paths.
    Keywords: ATK; Application; nanowires; BeO substrate; structural stability; transmission pathways; geometry optimization; band structure; conductance; adsorption; junctions; molecules; chains
    Area: nanowires
    BibTeX:
    @article{Barzilai2013e,
      author = {Barzilai, S and Tavazza, F and Levine, L E},
      title = {Structure stability and electronic transport of gold nanowires on a BeO (001) surface},
      journal = {Modelling and Simulation in Materials Science and Engineering},
      year = {2013},
      volume = {21},
      number = {7},
      pages = {075003},
      doi = {http://dx.doi.org/10.1088/0965-0393/21/7/075003}
    }
    
    Mausumi Chattopadhyaya, Sabyasachi Sen, Md.Mehboob Alam & Swapan Chakrabarti On site Coulomb repulsion dominates over the non-local Hartree-Fock exchange in determining the band gap of polymers 2014 Journal of Physics and Chemistry of Solids
    Vol. 75(2), 212-223 
    DOI  
    Abstract: The present study deals with the relative performance of the various density functional approaches in evaluating the band gap of polymer materials. Several density functional approximations that includes pure generalized gradient approximated (GGA) functional, meta-GGA, hybrid and range separated hybrid functionals have been used to evaluate the electrical band gap or transport gap of the studied polymers and compared with that obtained using Hubbard U corrected GGA functional (GGA+U). It has been observed that the experimental band gap of the polymers studied is satisfactorily reproducible when GGA+U approach is adopted. The band gap analyses further suggest that range separated hybrid functional, CAM-B3LYP, largely overestimates the band gap of all the polymers studied while the performance of hybrid B3LYP functional and other range separated hybrid functional like HSE is moderate. Better performance of the GGA+U method clearly indicates that short range coulomb correlation plays more significant role over the non-local Hartree-Fock (HF) exchange in determining the electrical band gap of polymer materials. It is also noticeable that the Hubbard U parameter used for the various polymers under consideration is relatively large, indicating the semi-empirical nature of the GGA+U level of calculations. The present finding will help us design new low band gap polymer through estimating band gap by the GGA+U method and this could be very useful for solar cell research.
    Keywords: ATK, Application, polymers, ab initio calculations, electronic structure
    Area: materials
    BibTeX:
    @article{Chattopadhyaya2014,
      author = {Chattopadhyaya, Mausumi and Sen, Sabyasachi and Alam, Md.Mehboob and Chakrabarti, Swapan},
      title = {On site Coulomb repulsion dominates over the non-local Hartree-Fock exchange in determining the band gap of polymers},
      journal = {Journal of Physics and Chemistry of Solids},
      year = {2014},
      volume = {75},
      number = {2},
      pages = {212--223},
      doi = {http://dx.doi.org/10.1016/j.jpcs.2013.09.018}
    }
    
    Daniel DeBrincat, Oliver Keers & John E. McGrady Can heterometallic 1-dimensional chains support current rectification? 2013 Chem. Commun.
    Vol. 49(80), 9116-9118 
    DOI  
    Abstract: To what extent can a heterometallic chain of transition metal ions generate an asymmetric current-voltage response? Density functional theory suggests that the answer depends very much on the symmetry of the dominant conduction channel: pi channels are more localised and hence afford higher rectification ratios.
    Keywords: ATK, Application, molecular electronics, rectification
    Area: molecular electronics
    BibTeX:
    @article{DeBrincat2013,
      author = {DeBrincat, Daniel and Keers, Oliver and McGrady, John E.},
      title = {Can heterometallic 1-dimensional chains support current rectification?},
      journal = {Chem. Commun.},
      publisher = {The Royal Society of Chemistry},
      year = {2013},
      volume = {49},
      number = {80},
      pages = {9116--9118},
      doi = {http://dx.doi.org/10.1039/C3CC45063E}
    }
    
    X.Q. Deng, Z.H. Zhang, C.H. Yang, H.L. Zhu & B. Liang The design of spin filter junction in zigzag graphene nanoribbons with asymmetric edge hydrogenation 2013 Organic Electronics
    Vol. 14(12), 3240-3248 
    DOI  
    Abstract: Using the non-equilibrium Green's function method combined with the density functional theory, we investigate the electronic transport properties of a heterostructure based on zigzag graphene, This heterostructure consists of H2-NZGNR-H and H-NZGNR-H. Results show that a perfect dual spin filtering effect can be realized with the parallel (P) and antiparallel (AP) magnetiesm configuration, and some magnetic domain walls (DW) at the interface between two component ribbons. The magnetic moments, DOS and PDOS, the transmission pathways and LDOS demonstrate that the edge of C-H2 bonds have important effects for magnetic and spin dependent transport properties compared to the edge of C-H bonds. Our results show that the H2-ZGNR-H/H-NZGNR-H heterostructure holds promise for magneto electronics devices which can keep steady properties when change the widths of the two component ribbons.
    Keywords: ATK, Application, Spin filtering effect, Graphene nanoribbons, Heterostructure, First-principles calculation
    Area: graphene; spin
    BibTeX:
    @article{Deng2013,
      author = {Deng, X.Q. and Zhang, Z.H. and Yang, C.H. and Zhu, H.L. and Liang, B.},
      title = {The design of spin filter junction in zigzag graphene nanoribbons with asymmetric edge hydrogenation},
      journal = {Organic Electronics},
      year = {2013},
      volume = {14},
      number = {12},
      pages = {3240--3248},
      doi = {http://dx.doi.org/10.1016/j.orgel.2013.09.041}
    }
    
    X.Q. Deng, Z.H. Zhang, G.P. Tang, Z.Q. Fan & C.H. Yang Spin filter effects in zigzag-edge graphene nanoribbons with symmetric and asymmetric edge hydrogenations 2014 Carbon
    Vol. 66(0), 646-653 
    DOI  
    Abstract: Using the non-equilibrium Greenâ's function method combined with the density functional theory, we investigate the magnetism and spin-dependent transport properties of symmetric and asymmetric zigzag-edged graphene nanoribbons (ZGNRs) passivated by monohydrogenation with [1, -1] magnetism configuration. The symmetric model H-6ZGNR-H shows a dual spin filter effect, but asymmetric H-5ZGNR-H behaves as a conductor with linear current-voltage relationships. We also investigate the magnetism and spin-dependent transport properties of H2-ZGNR-H with asymmetric edge hydrogenations, the perfect dual spin filtering effect is observed in both H2-5ZGNR-H and H2-6ZGNR-H. The transmission pathways and PDOS demonstrate that the edge of C-H2 bonds have important effects on the magnetism and spin-dependent transport properties as compared with the edge of C-H bonds.
    Keywords: ATK, Application, graphene nanoribbon, spin
    Area: graphene; spin
    BibTeX:
    @article{Deng2014,
      author = {Deng, X.Q. and Zhang, Z.H. and Tang, G.P. and Fan, Z.Q. and Yang, C.H.},
      title = {Spin filter effects in zigzag-edge graphene nanoribbons with symmetric and asymmetric edge hydrogenations},
      journal = {Carbon},
      year = {2014},
      volume = {66},
      number = {0},
      pages = {646--653},
      doi = {http://dx.doi.org/10.1016/j.carbon.2013.09.061}
    }
    
    Jing Huang, Weiyi Wang, Shangfeng Yang, Qunxiang Li & Jinlong Yang Spin-polarized transport properties of Mn@Au6 cluster 2013 Chemical Physics Letters
    Vol. 590(0), 111-115 
    DOI  
    Abstract: We explore the spin-polarized electronic structures and transport properties of Mn@Au6 cluster. The ab initio modeling is performed by combining the spin-polarized density functional theory with nonequilibrium Green's function formalism. Theoretical results clearly reveal that the central Mn atom anti-ferromagnetically couples with the Au6 ring and the cluster magnetic moment is 3.0 muB. The spin-resolved transmission spectra of Mn@Au6 sandwiched between two Li (1 0 0) electrodes exhibit robust spin filtering effect. The conductance of Mn@Au6 at the small bias voltage is mainly determined by the spin-up electrons. The findings indicate that Mn@Au6 cluster holds promise in molecular spintronics applications.
    Keywords: ATK; Application; molecular electronics; spin filtering; negative differential resistance (NDR); molecular junctions; density; device; approximation; spintronics; electronics; behavior; magnets
    Area: molecular electronics; spin
    BibTeX:
    @article{Huang2013a,
      author = {Huang, Jing and Wang, Weiyi and Yang, Shangfeng and Li, Qunxiang and Yang, Jinlong},
      title = {Spin-polarized transport properties of Mn@Au6 cluster},
      journal = {Chemical Physics Letters},
      year = {2013},
      volume = {590},
      number = {0},
      pages = {111--115},
      doi = {http://dx.doi.org/10.1016/j.cplett.2013.10.049}
    }
    
    Jianming Jia, Shin-Pon Ju, Daning Shi & Kuan-Fu Lin CO adsorption on a zigzag SiC nanotube: effects of concentration density and local torsion on transport 2013 Journal of Nanoparticle Research
    Vol. 15(10)Journal of Nanoparticle Research, 1977 
    DOI  
    Abstract: The electron transport properties of CO adsorbed SiC nanotubes as a function of concentration density and structural deformation have been characterized for the single-walled (7,0) zigzag model using a combined formalism of density-functional theory and nonequilibrium Green's function. It is found that CO adsorption can significantly suppress the transmission spectrum of SiC nanotube for a wide range of energies. As the concentration increases, a density-dependent superimposed transport gap exists and widens the initial electronic band gap of SiC nanotube. Under the same applied bias voltage, the current through SiC nanotube decreases with the increasing CO concentrations. The local torsional deformation has no effect on this essential motif. However, the current in the locally twisted system is larger than that of the undeformed one. The transmission suppression and the current differences can be attributed to the response of the localized impurity state induced by CO adsorption to density and deformation. Our results show that SiC nanotube can be a promising gas sensor for CO detection.
    Keywords: ATK; Application; SiC nanotube; CO molecules; adsorption; transport property; sensor; silicon-carbide nanotubes; carbon nanotubes; ab-initio; electronic-properties; gas sensors; molecules; functionalization; monoxide
    Area: nanotubes
    BibTeX:
    @article{Jia2013,
      author = {Jia, Jianming and Ju, Shin-Pon and Shi, Daning and Lin, Kuan-Fu},
      title = {CO adsorption on a zigzag SiC nanotube: effects of concentration density and local torsion on transport},
      booktitle = {Journal of Nanoparticle Research},
      journal = {Journal of Nanoparticle Research},
      publisher = {Springer Netherlands},
      year = {2013},
      volume = {15},
      number = {10},
      pages = {1977},
      doi = {http://dx.doi.org/10.1007/s11051-013-1977-7}
    }
    
    Dibyashree Koushik, Piyush Kumar Sinha, Neha Tyagi, R.K. Dey & Anurag Srivastava Electronic Properties of Hydrogen Terminated XO (X = Mn, Zn, Ca) Nanowires: Ab-Initio Study 2014 Quantum Matter
    Vol. 3(2), 134-145 
    DOI  
    Abstract: We have performed a DFT based ab-initio study to analyze the structural stability and electronic properties of hydrogen terminated XO (X = Mn, Zn and Ca) nanowires in their linear and zigzag geometries. The total minimum energy structures have been analyzed under revised Perdew-Burke-Ernzerhof (revPBE) type parameterized GGA potential. The stability of nanowires have been analysed with one end and both end hydrogen termination and a comparative analysis of with and without hydrogen terminated geometries in terms of structural stability, electronic band structure and density of states have been made. The study confirms the effect of hydrogen passivation on the electronic band structure, as in case of both ends H-terminated ZnO and CaO linear and zigzag configurations the band gap decreases whereas in case of MnO linear and zigzag configurations the band gap increases.
    Keywords: ATK, Application, ab-initio, CaO, electronic structure, hydrogen-termination, MnO, nanowire, ZnO
    Area: nanowires
    BibTeX:
    @article{Koushik2014,
      author = {Koushik, Dibyashree and Sinha, Piyush Kumar and Tyagi, Neha and Dey, R. K. and Srivastava, Anurag},
      title = {Electronic Properties of Hydrogen Terminated XO (X = Mn, Zn, Ca) Nanowires: Ab-Initio Study},
      journal = {Quantum Matter},
      year = {2014},
      volume = {3},
      number = {2},
      pages = {134--145},
      doi = {http://dx.doi.org/10.1166/qm.2014.1105}
    }
    
    Yu-Shen Liu, Xue-Feng Wang & Feng Chi Non-magnetic doping induced a high spin-filter efficiency and large spin Seebeck effect in zigzag graphene nanoribbons 2013 J. Mater. Chem. C
    Vol. 1(48), 8046-8051 
    DOI  
    Abstract: Based on nonequilibrium Green's functions (NGF) and density-functional theory (DFT), we investigate the magnetotransport properties and magnetothermoelectric effects in zigzag graphene nanoribbons (ZGNRs) with non-magnetic doping on the double ribbon edges. One of the carbon atoms without hydrogen saturation in each ribbon edge is replaced by one boron (B) or one nitrogen (N) atom. Compared with boron-boron (BB) and nitrogen-nitrogen (NN) double-edge doping, the boron-nitrogen (BN) double-edge doping induces a perfect spin-filter effect with 100% negative spin polarization at the Fermi level. Moreover, we find that the thermoelectric effect can be enhanced by the double-edge doping. Interestingly, the spin Seebeck effect in NN- and BN-doped ZGNRs becomes comparable with the charge Seebeck effect and even larger than it. These results originate from the spin-dependent transmission node near the Fermi level induced by the non-magnetic doping. These findings strongly suggest that the double-edge-doped ZGNRs are promising materials for spintronics and thermo-spintronics.
    Keywords: ATK, Application, graphene nanoribbon, spin, magnetotransport properties, magnetothermoelectric effects, Seebeck coefficient, doping
    Area: graphene; spin; thermo
    BibTeX:
    @article{Liu2013c,
      author = {Liu, Yu-Shen and Wang, Xue-Feng and Chi, Feng},
      title = {Non-magnetic doping induced a high spin-filter efficiency and large spin Seebeck effect in zigzag graphene nanoribbons},
      journal = {J. Mater. Chem. C},
      publisher = {The Royal Society of Chemistry},
      year = {2013},
      volume = {1},
      number = {48},
      pages = {8046--8051},
      doi = {http://dx.doi.org/10.1039/C3TC31537A}
    }
    
    Jie Ma, Chuan-Lu Yang, Li-Zhi Wang, Mei-Shan Wang & Xiao-Guang Ma Controllable low-bias negative differential resistance, switching, and rectifying behaviors of dipyrimidinyl-diphenyl induced by contact mode 2014 Physica B: Condensed Matter
    Vol. 434(0), 32-37 
    DOI  
    Abstract: The negative differential resistance (NDR) and the rectifying behaviors of a molecular device induced by a saturated hydrogen atom and contact modes are investigated. Results reveal low-bias NDR behaviors of dipyrimidinyl-diphenyl (DD) molecule without saturated H atoms. NDR behavior can be eliminated depending on the contact sites. However, the rectifying behaviors of DD-molecule with saturated H atoms are apparent for all considered contact modes. In addition, the possible contact mode of the molecule in the experiment [12] was identified by examining the effect of molecular adsorption sites on gold electrodes and saturated hydrogen atom on conductance. The mechanism underlying various properties are analyzed with the highest occupied molecular orbital, lowest unoccupied molecular orbital, and transmission spectra.
    Keywords: ATK, Application, switching, rectifying, negative differential resistance, NDR, contact sites, molecular electronics
    Area: molecular electronics
    BibTeX:
    @article{Ma2014,
      author = {Ma, Jie and Yang, Chuan-Lu and Wang, Li-Zhi and Wang, Mei-Shan and Ma, Xiao-Guang},
      title = {Controllable low-bias negative differential resistance, switching, and rectifying behaviors of dipyrimidinyl-diphenyl induced by contact mode},
      journal = {Physica B: Condensed Matter},
      year = {2014},
      volume = {434},
      number = {0},
      pages = {32--37},
      doi = {http://dx.doi.org/10.1016/j.physb.2013.10.039}
    }
    
    Y. Matsuura Spin transport in bimetallocene 2013 Journal of Applied Physics
    Vol. 114(10), 103707 
    DOI  
    Abstract: I present a theoretical study on the spin-transport behavior of bimetallocenes of cobalt or nickel, wherein electronic communication between the two metal centers can be efficiently performed via a fulvalene ligand. The transmission of electrons in the bimetallocene connected to two gold electrodes was calculated using a first-principles density functional method. Spin transport was estimated from the difference between the transmissions of the spin-up and spin-down states. Results revealed that bicobaltocene has a perfect spin-filtering effect because the supply of excess electrons to the electronic state of ferrocene causes a split in the energy levels of the spin-up and spin-down states. As surmised, it was found that spin polarization was caused by strong interactions between the two metal centers via the fulvalene ligand. Furthermore, bicobaltocene exhibited a negative differential resistance at a relatively low bias voltage.
    Keywords: ATK, Application, spin polarised transport, molecular electronics
    Area: molecular electronics; spin
    BibTeX:
    @article{Matsuura2013b,
      author = {Matsuura, Y.},
      title = {Spin transport in bimetallocene},
      journal = {Journal of Applied Physics},
      year = {2013},
      volume = {114},
      number = {10},
      pages = {103707},
      doi = {http://dx.doi.org/10.1063/1.4821041}
    }
    
    Y. Min, J.H. Fang, Z.C. Dong, C.G. Zhong, C.P. Chen & K.L. Yao Disconnected zigzag carbon nanotube as spin valve and spin filter predicted by first-principles study 2013 Physica B: Condensed Matter
    Vol. 430(0), 40-44 
    DOI  
    Abstract: The first-principles study of the spin-polarized transport of a disconnected zigzag carbon nanotube is reported. We find that the tunnel magnetoresistance ratio continuously increases and has no trend of decrease. For magnetic parallel configuration, the spin-filter ratio also increases with bias and eventually reaches 99.37%. Our results indicate that the disconnected zigzag carbon nanotubes can be used as a perfect spin-filter or spin valve.
    Keywords: ATK, Application, first-principles, carbon nanotube, magnetic properties, defects, transport properties, nonequilibrium Green's-function
    Area: nanotubes; spin
    BibTeX:
    @article{Min2013,
      author = {Min, Y. and Fang, J.H. and Dong, Z.C. and Zhong, C.G. and Chen, C.P. and Yao, K.L.},
      title = {Disconnected zigzag carbon nanotube as spin valve and spin filter predicted by first-principles study},
      journal = {Physica B: Condensed Matter},
      year = {2013},
      volume = {430},
      number = {0},
      pages = {40--44},
      doi = {http://dx.doi.org/10.1016/j.physb.2013.08.027}
    }
    
    Y. Min, J.H. Fang, C.G. Zhong, Z.C. Dong, C.P. Chen & K.L. Yao Disconnect armchair carbon nanotube as rectifier predicted by first-principles study 2014 Computational Materials Science
    Vol. 81(0), 418-422 
    DOI  
    Abstract: For electronics devices based on carbon nanotube, we propose that the localization of the density of the states can enhance the rectification effect. The proposal is confirmed according to the first-principles study of the transport characteristics of several disconnected armchair nanotubes where only one side of armchair edge is hydrogenated. We find that the rectification effect increases as the diameter of armchair carbon nanotube and has no trend of decrease, which originates from the localization of the density of states of the pristine armchair edge. Our investigations indicate that the quantum size effect is helpful for molecular or nano-scale electronics devices.
    Keywords: ATK, Application, first-principles, non-equilibrium Green's-function, density-functional theory, carbon nanotube, molecular diode
    Area: nanotubes
    BibTeX:
    @article{Min2014,
      author = {Min, Y. and Fang, J.H. and Zhong, C.G. and Dong, Z.C. and Chen, C.P. and Yao, K.L.},
      title = {Disconnect armchair carbon nanotube as rectifier predicted by first-principles study},
      journal = {Computational Materials Science},
      year = {2014},
      volume = {81},
      number = {0},
      pages = {418--422},
      doi = {http://dx.doi.org/10.1016/j.commatsci.2013.08.048}
    }
    
    Fangping Ouyang, Zhixiong Yang, Shenglin Peng, Xiaojuan Zheng & Xiang Xiong Antidot-dependent bandgap and Clar sextets in graphene antidot lattices 2014 Physica E: Low-dimensional Systems and Nanostructures
    Vol. 56(0), 222-226 
    DOI  
    Abstract: By using first-principles calculations, the bandgap of two types of graphene antidot lattices (GALs) with triangular lattice, anthrancene-removed GALs and phenanthrene-removed GALs, have been studied. One third of either GALs are semiconductors as lattice parameter varies, while the lattice parameters corresponding to semiconductors are different in the two GALs, indicating the bandgap opening of GALs depends on the antidot configuration as well as lattice parameter. The bandgap opening or not is interpreted with Clar's aromatic sextet theory. A nonzero bandgap appears in phenanthrene-removed GALs, only when the number of Clar sextets exceeds one third of the total number of hexagons in the unit cell. However, due to a long zigzag edge existing in anthrancene-removed GALs, the bandgap can be open without meeting the condition. Our results suggest that the antidot configuration is a non negligible factor on the bandgap of graphene antidot lattices.
    Keywords: ATK, Application, Graphene superlattices, Antidot, Bandgap, Clar sextets, First-principles
    Area: graphene
    BibTeX:
    @article{Ouyang2014,
      author = {Ouyang, Fangping and Yang, Zhixiong and Peng, Shenglin and Zheng, Xiaojuan and Xiong, Xiang},
      title = {Antidot-dependent bandgap and Clar sextets in graphene antidot lattices},
      journal = {Physica E: Low-dimensional Systems and Nanostructures},
      year = {2014},
      volume = {56},
      number = {0},
      pages = {222--226},
      doi = {http://dx.doi.org/10.1016/j.physe.2013.09.006}
    }
    
    Feng Pan, Ruge Quhe, Qi Ge, Jiaxin Zheng, Zeyuan Ni, Yangyang Wang, Zhengxiang Gao, Lu Wang & Jing Lu Gate-induced half-metallicity in semihydrogenated silicene 2014 Physica E: Low-dimensional Systems and Nanostructures
    Vol. 56(0), 43-47 
    DOI  
    Abstract: The first-principles calculations indicate that the semihydrogenated silicene (H@Silicene) is a ferromagnetic semiconductor. By the ab initio quantum transport theory, we study for the first time the transport properties of H@Silicene with pristine silicene as electrodes. A high on/off current ratio of 106 is obtained in the single-gated H@Silicene device. More importantly, a spin-polarized current can be generated. The spin-filter efficiency increases with the gate voltage and reaches 100% at a voltage of 1.9 V. Our results suggest that a gate voltage can induce half-metallicity in H@Silicene. Therefore, a new avenue is opened for H@Silicene in application of spintronics.
    Keywords: ATK, Application, silicene, half-metallicity, quantum transport, first-principles calculation, spin-polarized transport
    Area: graphene; spin
    BibTeX:
    @article{Pan2014,
      author = {Pan, Feng and Quhe, Ruge and Ge, Qi and Zheng, Jiaxin and Ni, Zeyuan and Wang, Yangyang and Gao, Zhengxiang and Wang, Lu and Lu, Jing},
      title = {Gate-induced half-metallicity in semihydrogenated silicene},
      journal = {Physica E: Low-dimensional Systems and Nanostructures},
      year = {2014},
      volume = {56},
      number = {0},
      pages = {43--47},
      doi = {http://dx.doi.org/10.1016/j.physe.2013.08.011}
    }
    
    Pabitra Narayan Samanta & Kalyan Kumar Das Electron transport properties of zigzag single walled tin carbide nanotubes 2014 Computational Materials Science
    Vol. 81(0), 326-331 
    DOI  
    Abstract: A combined method of density functional theory and non-equilibrium Green's function formalism has been used to study the electron transport properties of zigzag single walled SnC nanotubes (SnCNTs) of different chiralities. Band structures of zigzag SnCNTs from (4, 0) to (6, 0) are calculated using 1 x 1 x 100 k-point sampling. Transmission coefficients are computed for (n, 0) SnCNT (n = 4, 5, 6) devices at various positive and negative bias voltages within +-2.4 V. The current-voltage (I-V) curves in this bias voltage region show negative differential resistance (NDR), which is analyzed from the transmission spectra and molecular projected self-consistent Hamiltonian (MPSH) states. The rectifying performances of these devices are investigated by calculating the rectification ratio (I+/I-) with the bias voltage.
    Keywords: ATK, Application, tin-carbide nanotubes, transmission spectra, I-V curves, NDR effects, MPSH
    Area: nanotubes
    BibTeX:
    @article{Samanta2014,
      author = {Samanta, Pabitra Narayan and Das, Kalyan Kumar},
      title = {Electron transport properties of zigzag single walled tin carbide nanotubes},
      journal = {Computational Materials Science},
      year = {2014},
      volume = {81},
      number = {0},
      pages = {326--331},
      doi = {http://dx.doi.org/10.1016/j.commatsci.2013.08.035}
    }
    
    Ravinder Singh Sawhney, Harsimran Kaur & Derick Engles Effect of the Electrodes Material on Electron Transport Through Molecular Junctions 2014 Quantum Matter
    Vol. 3(2), 127-133 
    DOI  
    Abstract: In this paper, we anatomized the influence of changing the material of electrodes on the transport properties of single molecular junction comprising acetone molecule stringed to two semi-infinite electrodes using semi empirical model. The investigation of electron transport through acetone molecule was accomplished by linking it to different metallic electrodes (Pt, Pd, Au and Ag) and a non-metallic electrode (carbon) under different bias voltages within Keldysh's non-equilibrium Green Function formulism (NEGF) using Extended Hückel (EHT) semi empirical approach. The simulated results revealed that among metallic and non-metallic electrodes, the metallic electrodes showed maximum conductance of the order of 10^-6 nS, whereas non-metallic electrodes showed conductance of the order of 10^-16 nS which is in confirmation with the results proved by other authors. By comparing the I-V curves obtained using different metallic electrodes, we perceived that gold showed maximum conductance and transmission of current amidst strongest coupling and thus affirmed to be the most effective material for electrodes for nanometer scale molecular junctions, when compared with other metallic electrodes viz. platinum, palladium, and silver.
    Keywords: ATK-SE, Application, scanning tunnelling microscope (STM), mechanically controllable break junctions (MCBJ), self-assembled mono layers (SAM), extended Huckel theory (EHT), non equilibrium Green's function (NEGF), molecular electronics
    Area: molecular electronics
    BibTeX:
    @article{Sawhney2014,
      author = {Sawhney, Ravinder Singh and Kaur, Harsimran and Engles, Derick},
      title = {Effect of the Electrodes Material on Electron Transport Through Molecular Junctions},
      journal = {Quantum Matter},
      year = {2014},
      volume = {3},
      number = {2},
      pages = {127--133},
      doi = {http://dx.doi.org/10.1166/qm.2014.1104}
    }
    
    Anurag Srivastava, Srashti Jain & A.K. Nagawat Electronic Properties of Nitrogen Doped Armchair Single Wall Nanotubes: Ab-Initio Study 2013 Quantum Matter
    Vol. 2(6), 469-473 
    DOI  
    Abstract: We have analysed the effect of nitrogen doping on electronic properties of the armchair SWCNT, using density functional theory based Atomistix ToolKit (ATK) Virtual NanoLab (VNL). The total energy calculation has been performed using generalized gradient approximation (GGA) as exchange correlation functional. Findings reveal that the introduction of two and six atoms of nitrogen at the edge of armchair SWCNT changes its metallic behavior to semiconducting and unchanged for others in the nitrogen atoms range of 0<=n<=6.
    Keywords: ATK, Application, ab-initio, armchair, electronic properties, nitrogen, single-walled carbon nanotube
    Area: nanotubes
    BibTeX:
    @article{Srivastava2013e,
      author = {Srivastava, Anurag and Jain, Srashti and Nagawat, A. K.},
      title = {Electronic Properties of Nitrogen Doped Armchair Single Wall Nanotubes: Ab-Initio Study},
      journal = {Quantum Matter},
      year = {2013},
      volume = {2},
      number = {6},
      pages = {469--473},
      doi = {http://dx.doi.org/10.1166/qm.2013.1083}
    }
    
    Kurt Stokbro & Soren Smidstrup Electron transport across a metal-organic interface: Simulations using nonequilibrium Green's function and density functional theory 2013 Physical Review B
    Vol. 88(7), 075317 
    DOI  
    Abstract: We simulate the electron transport across the Au(111)-pentacene interface using nonequilibrium Green's functions and density-functional theory (NEGF-DFT), and calculate the bias-dependent electron transmission. We find that the electrical contact resistance is dominated by the formation of a Schottky barrier at the interface, and show that the conventional semiconductor transport models across Schottky barriers need to be modified in order to describe the simulation data. We present an extension of the conventional Schottky barrier transport model, which can describe our simulation results and rationalize recent experimental data.
    Keywords: ATK, Application, metal-organic interface, Schottky barrier formation, experimental comparison
    Area: molecular electronics; interfaces
    BibTeX:
    @article{Stokbro2013,
      author = {Stokbro, Kurt and Smidstrup, Soren},
      title = {Electron transport across a metal-organic interface: Simulations using nonequilibrium Green's function and density functional theory},
      journal = {Physical Review B},
      publisher = {American Physical Society},
      year = {2013},
      volume = {88},
      number = {7},
      pages = {075317},
      doi = {http://dx.doi.org/10.1103/PhysRevB.88.075317}
    }
    
    K Stokbro, A Blom & S Smidstrup Atomistic simulation of a III-V p-i-n junction 2013 SISPAD, 380-383   
    Abstract: We compare the results of calculations based on tight-binding and density functional theory (DFT) for the description of an ultra-narrow two-dimensional (2D) InAs system. We first investigate the electronic structure of the 2D system to understand the effect of different surface terminations and how they are modeled using tight-binding and DFT approaches. We next set up a gated 2D InAs p-i-n junction and calculate the transistor characteristics of the system using the two different approaches.
    Keywords: ATK; Application; semiconductor; InAs; doping; transistor characteristics; FinFET
    Area: semi
    BibTeX:
    @inproceedings{Stokbro2013a,
      author = {K Stokbro and A Blom and S Smidstrup},
      title = {Atomistic simulation of a III-V p-i-n junction},
      booktitle = {SISPAD},
      year = {2013},
      pages = {380-383}
    }
    
    Qing-Qing Sun, Lu-Hao Wang, Wen Yang, Peng Zhou, Peng-Fei Wang, Shi-Jin Ding & David Wei Zhang Atomic Scale Investigation of a Graphene Nano-ribbon Based High Efficiency Spin Valve 2013 Sci. Rep.
    Vol. 3, 2921 
    DOI  
    Abstract: Graphene nanoribbons based electronic devices present many interesting physical properties. We designed and investigated the spin-dependent electron transport of a device configuration, which is easy to be fabricated, with an oxygen-terminated ZGNR central scatter region between two hydrogen-terminated ZGNR electrodes. According to the analysis based on non-equilibrium Green's function and density functional theory, the proposed device could maintain its good spin-filter performance (80% to 99%) and have a stable magneto resistance value up to 105%. The spin dependent electron transmission spectrum and space-resolve density of states are employed to investigate the physical origin of the spin-polarized current and magneto resistance.
    Keywords: ATK; Application; graphene nanoribbon; spin filter; magnetoresistance; devices
    Area: graphene; spin
    BibTeX:
    @article{Sun2013a,
      author = {Sun, Qing-Qing and Wang, Lu-Hao and Yang, Wen and Zhou, Peng and Wang, Peng-Fei and Ding, Shi-Jin and Zhang, David Wei},
      title = {Atomic Scale Investigation of a Graphene Nano-ribbon Based High Efficiency Spin Valve},
      journal = {Sci. Rep.},
      publisher = {Macmillan Publishers Limited. All rights reserved},
      year = {2013},
      volume = {3},
      pages = {2921},
      doi = {http://dx.doi.org/10.1038/srep02921}
    }
    
    Q.H. Wu, P. Zhao, D.S. Liu & G. Chen Magnetoresistance, spin filtering and negative differential resistance effects in an endohedral Fe@C60 dimer 2013 Solid State Communications
    Vol. 174(0), 5-9 
    DOI  
    Abstract: Based on non-equilibrium Green's method and density functional theory, the spin-polarized transport properties of an endohedral Fe@C60 dimer-based spintronic device are investigated. The direction of the magnetic moments of the two Fe atoms can be controlled by applying a magnetic field. The interesting magnetoresistance, spin filtering and negative differential resistance effects can be observed in this device. These phenomena are explained by the evolution of spin-dependent transmission spectra and projected density of states with the increase in bias, as well as the voltage drop distributions.
    Keywords: ATK, Application, fullerene dimer, magnetoresistance effect, spin filtering effect, negative differential resistance (NDR), giant magnetoresistance; transport-properties; 1st-principles; spintronics; electronics
    Area: fullerenes; spin
    BibTeX:
    @article{Wu2013b,
      author = {Wu, Q.H. and Zhao, P. and Liu, D.S. and Chen, G.},
      title = {Magnetoresistance, spin filtering and negative differential resistance effects in an endohedral Fe@C60 dimer},
      journal = {Solid State Communications},
      year = {2013},
      volume = {174},
      number = {0},
      pages = {5--9},
      doi = {http://dx.doi.org/10.1016/j.ssc.2013.09.020}
    }
    
    Serhan Yamacli First principles study of the voltage-dependent conductance properties of n-type and p-type graphene-metal contacts 2014 Computational Materials Science
    Vol. 81(0), 607-611 
    DOI  
    Abstract: Abstract Investigation of the conductance properties of metal-graphene contacts is essential for the future nanoelectronics technology. In this study, we focus on the conductance mechanism and the voltage-dependent transport properties of both p-type and n-type graphene-metal contacts. Copper and gold are chosen as the contact metal for n-type and p-type doped graphene-metal interface, respectively. Utilizing first principles quantum mechanical calculations with density functional theory in conjunction with Green's function formalism, transmission spectra of graphene-metal contacts and the voltage-dependent variations of the current and the resistance are obtained. Finally, it is shown that obtained resistance-voltage behaviours of graphene-metal contacts are in consistent with the results reported in the literature and the voltage-dependency of the contact resistance has to be taken into consideration for the nanoscale circuit design process.
    Keywords: ATK, Application, Graphene, Metal contact, Conductance, Transmission spectrum
    Area: graphene
    BibTeX:
    @article{Yamacli2014,
      author = {Yamacli, Serhan},
      title = {First principles study of the voltage-dependent conductance properties of n-type and p-type graphene-metal contacts},
      journal = {Computational Materials Science},
      year = {2014},
      volume = {81},
      number = {0},
      pages = {607--611},
      doi = {http://dx.doi.org/10.1016/j.commatsci.2013.09.015}
    }
    
    Zhi Yang, Baolong Zhang, Xuguang Liu, Yongzhen Yang, Xiuyan Li, Shijie Xiong & Bingshe Xu The spin-filter capability and giant magnetoresistance effect in vanadium-naphthalene sandwich cluster 2013 Organic Electronics
    Vol. 14(11), 2916-2924 
    DOI  
    Abstract: Using density functional theory and non-equilibrium Green's function technique, we performed theoretical investigations on the magnetic and transport properties of V2n(C10H8)n+1 (n = 1-4) sandwich clusters. For the ground states, our results show that all the clusters are stable and possess ferromagnetic orders. The smaller clusters have higher stabilities, and our predictions are in agreement with the experimental observation. The double exchange mechanism plays an important role in determining the magnetic properties of the systems. Furthermore, with Ni as electrodes, the clusters exhibit interesting transport properties such as significant spin-filter capability, negative differential resistance feature and giant magnetoresistance effect. These findings suggest that V2n(C10H8)n+1 sandwiches are excellent candidates for application in spintronics and organic electronics.
    Keywords: ATK; Application; sandwich cluster; spin-filter capability; giant magnetoresistance; negative differential resistance (NDR); magnetic properties; ionization energies; Stern Gerlach; benzene; complexes; ferromagnetism; nanowires; transport; metals
    Area: molecular electronics; spin
    BibTeX:
    @article{Yang2013b,
      author = {Yang, Zhi and Zhang, Baolong and Liu, Xuguang and Yang, Yongzhen and Li, Xiuyan and Xiong, Shijie and Xu, Bingshe},
      title = {The spin-filter capability and giant magnetoresistance effect in vanadium-naphthalene sandwich cluster},
      journal = {Organic Electronics},
      year = {2013},
      volume = {14},
      number = {11},
      pages = {2916--2924},
      doi = {http://dx.doi.org/10.1016/j.orgel.2013.08.016}
    }
    
    Demin Yin, Weihua Liu, Xin Li, Li Geng, Xiaoli Wang & Pu Huai Mono-bi-monolayer graphene junction introduced quantum transport channels 2013 Applied Physics Letters
    Vol. 103(17), 173519 
    DOI  
    Abstract: Quantum transport properties of mono-bi-monolayer graphene junctions (MBMGJs) are investigated via first principle calculation. The simulation results show that the MBMGJs introduce more effective quantum transport channels in comparing with a full monolayer graphene nanoribbon channel and result in significantly increased on-state current. An overlapping-MBMGJ channel with one overlapping zigzag carbon chain shows a larger current even than a full bilayer graphene channel. The robustness of the effective quantum transport channel introduced by the overlapping-MBMGJ against the variation of the length of the bilayer region is also verified.
    Keywords: ATK; Application; graphene; bilayer; monolayer; MPSH
    Area: graphene
    BibTeX:
    @article{Yin2013,
      author = {Yin, Demin and Liu, Weihua and Li, Xin and Geng, Li and Wang, Xiaoli and Huai, Pu},
      title = {Mono-bi-monolayer graphene junction introduced quantum transport channels},
      journal = {Applied Physics Letters},
      year = {2013},
      volume = {103},
      number = {17},
      pages = {173519},
      doi = {http://dx.doi.org/10.1063/1.4826694}
    }
    
    J.J. Zhang, Z.H. Zhang, J. Li, D. Wang, Z. Zhu, G.P. Tang, X.Q. Deng & Z.Q. Fan Enhanced half-metallicity in carbon-chain-linked trigonal graphene 2014 Organic Electronics
    Vol. 15(1), 65-70 
    DOI  
    Abstract: The spin polarization property of a zigzag-edge trigonal graphene (ZTG) linked with different-length carbon chains Cn is investigated theoretically. It has been found that the enhancement of such a property completely depends on that the number of carbon atoms in a chain being odd or even. If it is an even number, the spin polarization is only changed slightly due to the nearly nonmagnetic property of these carbon chains. In contrast, while it is an odd number, the spin polarization is enhanced significantly to a larger energy range, i.e., showing a prominent half-metallicity and perfect spin-filter effects, owing to interactions of the ZTG and carbon chains with the strong ferromagnetism property. Deepgoing analyses show that these results are intimately related to a polyyne-like configuration for carbon chains in nanojunctions and the transition from the bipolar magnetic semiconductor to half-metallicity. Our findings suggest that this simple structure might promise importantly potential applications for developing nano-scale spintronics devices.
    Keywords: ATK, Application, trigonal graphene, carbon chain, spin polarization, half-metallicity, MPSH
    Area: graphene; spin
    BibTeX:
    @article{Zhang2014,
      author = {Zhang, J.J. and Zhang, Z.H. and Li, J. and Wang, D. and Zhu, Z. and Tang, G.P. and Deng, X.Q. and Fan, Z.Q.},
      title = {Enhanced half-metallicity in carbon-chain-linked trigonal graphene},
      journal = {Organic Electronics},
      year = {2014},
      volume = {15},
      number = {1},
      pages = {65--70},
      doi = {http://dx.doi.org/10.1016/j.orgel.2013.10.022}
    }
    
    P. Zhao, D.S. Liu & G. Chen Energy alignment induced large rectifying behavior in endoheral fullerene dimers 2013 The Journal of Chemical Physics
    Vol. 139(8), 084318 
    DOI  
    Abstract: Using the nonequilibrium Green's function formalism combined with density functional theory for quantum transport calculation, we have investigated the electronic transport properties of three endofullerenes Na@C60C60@F, Na@C60C60, and F@C60C60. The results show that the electronic transport properties of these endofullerenes are strongly dependent upon the species inside the fullerene. A large rectifying behavior is observed in Na@C60C60, while Na@C60C60@F and F@C60C60 can only present very weak rectification. It is revealed that the alignment between the molecular levels of two C60s moieties with the applied bias is the main cause of the large rectification in Na@C60C60.
    Keywords: ATK, Application, density functional theory, fullerenes, molecular electronics
    Area: fullerenes; molecular electronics
    BibTeX:
    @article{Zhao2013f,
      author = {Zhao, P. and Liu, D. S. and Chen, G.},
      title = {Energy alignment induced large rectifying behavior in endoheral fullerene dimers},
      journal = {The Journal of Chemical Physics},
      year = {2013},
      volume = {139},
      number = {8},
      pages = {084318},
      doi = {http://dx.doi.org/10.1063/1.4818746}
    }
    
    Yan-Hong Zhou, Jing Zeng, Li-Ming Tang, Ke-Qiu Chen & W.P. Hu Giant magnetoresistance effect and spin filters in phthalocyanine-based molecular devices 2013 Organic Electronics
    Vol. 14(11), 2940-2947 
    DOI  
    Abstract: The spin transport properties of molecular devices constructed by hydrogen-phthalocyanine and transition metal (TM)-phthalocyanine molecule with zigzag graphene nanoribbon electrodes are investigated by the Keldysh nonequilibrium Green's function method in combination with the density functional theory. The results show that there exists giant magnetoresistance in both the hydrogen-phthalocyanine and the TM-phthalocyanine systems. The magnetoresistance ratio is much bigger than that found by Schmaus et al. [S. Schmaus, A. Bagrets, Y. Nahas, T. K. Yamada, A. Bork, M. Bowen, E. Beaurepaire, F. Evers, W. Wulfhekel, Nature Nanotechnology 6 (2011) 185-189] in single hydrogen-phthalocyanine-Co electrodes system. Moreover, it is found that the chromium-phthalocyanine molecular device is a good spin filtering device with nearly 100% spin filtering efficiency at a wide bias voltage region. The mechanisms are proposed for these phenomena.
    Keywords: ATK; Application; giant magnetoresistance; spin filter; phthalocyanine molecule; density functional theory; spintronic devices; single molecule; rectification
    Area: graphene; spin
    BibTeX:
    @article{Zhou2013,
      author = {Zhou, Yan-Hong and Zeng, Jing and Tang, Li-Ming and Chen, Ke-Qiu and Hu, W.P.},
      title = {Giant magnetoresistance effect and spin filters in phthalocyanine-based molecular devices},
      journal = {Organic Electronics},
      year = {2013},
      volume = {14},
      number = {11},
      pages = {2940--2947},
      doi = {http://dx.doi.org/10.1016/j.orgel.2013.08.023}
    }
    
    Neeraj Jain, S. Manhas, A.K. Aggarwal & P.K. Chaudhry Effect of Metal Contact on CNT Based Sensing of NO2 Molecules 2014 Environmental Science and Engineering, 637-639-  DOI  
    Abstract: The electronic structure of Carbon Nanotubes (CNTs) is highly sensitive to the presence of foreign molecules. Also due to the large surface area of CNTs, there is a higher chance of them getting exposed to the surrounding gas molecules. This property is utilized in CNT based gas sensing applications. In this work, we have studied a zigzag CNT (Z-CNT) and simulated the transmission spectra and I-V characteristics using Density functional theory and Extended Huckel theory. Then the change in electrical properties of the Platinum (Pt) contacted Z-CNT on adsorption of NO2 molecules was simulated. Exposure of NO2 increases the conductance of the CNT by extracting electrons from the CNT making it p-type. Higher concentration of gas molecules results in larger change in the conductance due to the accumulated effects of individual gas molecules underlining its effectiveness in the formation of a gas sensor. Pt makes a schottky contact with the zigzag CNT and it was found that there is an appreciable change in the transmission spectrum as well as I-V characteristics making Platinum contacted zigzag CNT a good material for NO2 detection. This study is aimed at understanding effect of adsorption of NO2 and Pt contact on the I-V characteristics.
    Keywords: ATK; ATK-SE; Application; CNT based sensor, CNT-metal contact; Schottky barrier
    Area: nanotubes
    BibTeX:
    @incollection{Jain2014,
      author = {Jain, Neeraj and Manhas, S. and Aggarwal, A.K. and Chaudhry, P.K.},
      title = {Effect of Metal Contact on CNT Based Sensing of NO2 Molecules},
      booktitle = {Environmental Science and Engineering},
      publisher = {Springer International Publishing},
      year = {2014},
      pages = {637-639--},
      doi = {http://dx.doi.org/10.1007/978-3-319-03002-9_162}
    }
    
    Chao Jiang, Xue-Feng Wang & Ming-Xing Zhai Spin negative differential resistance in edge doped zigzag graphene nanoribbons 2014 Carbon
    Vol. 68(3), 406-412 
    DOI  
    Abstract: Abstract The nonlinear spin-dependent transport properties in zigzag graphene nanoribbons (ZGNRs) edge doped by an atom of group III and V elements are studied systematically using density functional theory combined with non-equilibrium Green's functions. The dopant type, acceptor or donor, and the geometrical symmetry, odd or even, are found critical in determining the spin polarization of the current and the current-voltage characteristics. For ZGNRs substitutionally doped on the lower-side edge, the down (up) spin current dominates in odd-(even-) width ZGNRs under a bias voltage around 1 V. Remarkably, in even-width ZGNRs, doped by group III elements (B and Al), negative differential resistance (NDR) occurs only for down spins. The bias range of the spin NDR increases with the width of ZGNRs. The clear spin NDR is not observed in any odd-width ZGNRs nor in even-width ZGNRs doped by group V elements (N and P). This peculiar spin NDR of edge doped ZGNRs suggests potential applications in spintronics.
    Keywords: ATK; Application; graphene; negative differential resistance; NDR; spin
    Area: graphene; spin
    BibTeX:
    @article{Jiang2014,
      author = {Jiang, Chao and Wang, Xue-Feng and Zhai, Ming-Xing},
      title = {Spin negative differential resistance in edge doped zigzag graphene nanoribbons},
      journal = {Carbon},
      year = {2014},
      volume = {68},
      number = {3},
      pages = {406--412},
      doi = {http://dx.doi.org/10.1016/j.carbon.2013.11.017}
    }
    
    Ivan P. Krotnev Novel metallic field-effect transistors 2013 School: University of Toronto  URL 
    Abstract: This thesis describes a novel concept for a field-effect transistor based on metallic channels. Latest research demonstrates that the bulk (3D) properties of many materials begin to change when confined to 2D sheets, or 1D nanowires. Particularly, the bandgap increases and the density of states decreases. In this work, this effect is explored further to demonstrate its application to field-effect transistors. Certain metals such as Gold and Silver in these dimensions have extremely low density of states in particular energy regions and through gate modulation can be partially depleted from electrons thus creating conditions for field-effect. A simulation study of Gold channel FET demonstrates ION=IOF F of 30 and superior current driving capability compared to the state-of-the art 22 nm SiGe ETSOI as well as 30 nm nanotube transistors.
    Keywords: ATK; Application; semi; field-effect transistor; metallic channel;
    Area: semi
    BibTeX:
    @phdthesis{Krotnev2013,
      author = {Ivan P. Krotnev},
      title = {Novel metallic field-effect transistors},
      school = {University of Toronto},
      year = {2013},
      url = {https://tspace.library.utoronto.ca/bitstream/1807/42990/3/Krotnev_Ivan_P_201311_MASc_thesis.pdf}
    }
    
    Meng-Qiu Long, Xin-Mei Li, Jun He, Bingchu Yang & Liling Cui Electronic transport properties of transition metal (Cu, Fe) phthalocyanines connecting to v-shaped zigzag graphene nanoribbons 2014 International Journal of Modern Physics B
    Vol. 28(0), 1450019 
    DOI  
    Abstract: Using nonequlilibrium Green's functions in combination with the density-functional theory, we investigate the spin transport properties of molecular junction based on metal (Cu, Fe) phthalocyanines between V-shaped zigzag-edged graphene nanorribons. The results show that the electronic transport properties mainly depend on the center transition metal. The negative differential resistance behaviors and spin splitting phenomenon can be observed.
    Keywords: ATK; Application; graphene; molecular electronics; spin-polarized transport
    Area: graphene; spin
    BibTeX:
    @article{Long2014,
      author = {Long, Meng-Qiu and Li, Xin-Mei and He, Jun and Yang, Bingchu and Cui, Liling},
      title = {Electronic transport properties of transition metal (Cu, Fe) phthalocyanines connecting to v-shaped zigzag graphene nanoribbons},
      journal = {International Journal of Modern Physics B},
      year = {2014},
      volume = {28},
      number = {0},
      pages = {1450019},
      doi = {http://dx.doi.org/10.1142/S0217979214500192}
    }
    
    Francisco J. Martin-Martinez, Stijn Fias, Balazs Hajgato, Gregory Van Lier, Frank De Proft & Paul Geerlings. Inducing Aromaticity Patterns and Tuning the Electronic Transport of Zigzag Graphene Nanoribbons via Edge Design 2013 J. Phys. Chem. C
    Vol. 117(49)The Journal of Physical Chemistry C, 26371-26384 
    DOI  
    Abstract: Despite its remarkable electronic properties, graphene is a semimetal, or zero-band-gap semiconductor, which limits its potential applications in electronics. Cutting graphene into nanoribbons is one of the most successful approaches to opening the band gap of graphene toward applications. However, whereas armchair graphene nanoribbons exhibit semiconducting behavior, zigzag-edged structures are still semimetals. In this work, we perform periodic density functional theory (DFT) calculations on the electronic structure, together with nonequilibrium Green's function (NEGF) transport-property calculations, of different tailored-edge zigzag graphene nanoribbons. More precisely, we provide a complete description of the relation between band gap, transport properties, and aromaticity distribution along these materials, based on DFT results and Clar's sextet theory. The edge design is also shown to be applicable for finite fragments of carbon nanotubes in which the electronic confinement is similar. This ansatz provides different methods for the rational edge design of zigzag graphene nanoribbons, which induces aromaticity patterns and opens the band gap toward electronic applications. The mean bond length (MBL) geometric parameter and the six-center index (SCI) aromaticity descriptor are used to analyze the aromaticity patterns.
    Keywords: ATK; Application; graphene nanoribbon; current density
    Area: graphene
    BibTeX:
    @article{Martin-Martinez2013,
      author = {Martin-Martinez, Francisco J. and Fias, Stijn and Hajgato, Balazs and Van Lier, Gregory and De Proft, Frank and Geerlings., Paul},
      title = {Inducing Aromaticity Patterns and Tuning the Electronic Transport of Zigzag Graphene Nanoribbons via Edge Design},
      booktitle = {The Journal of Physical Chemistry C},
      journal = {J. Phys. Chem. C},
      publisher = {American Chemical Society},
      year = {2013},
      volume = {117},
      number = {49},
      pages = {26371--26384},
      doi = {http://dx.doi.org/10.1021/jp410032h}
    }
    
    Wanzhi Qiu, Phuong Nguyen & Efstratios Skafidas Graphene nanopores: electronic transport properties and design methodology 2014 Phys. Chem. Chem. Phys.
    Vol. 16(4), 1451-1459 
    DOI  
    Abstract: Graphene nanopores (GNPs) hold great promise as building blocks for electronic circuitry and sensors for biological and chemical sensing applications. Methods to design graphene nanopores that achieve desirable conduction performance and sensing characteristics have not been previously described. Here we present a study of the quantum transport properties of GNPs created by drilling pores in armchair and zigzag graphene ribbons. For the first time, our study reveals that the quantum transmission spectra of GNPs are highly tunable and GNPs with specific transport properties can be produced by properly designing pore shapes. Our investigation shows that the biological sensing capabilities of GNPs are transmission spectrum dependent, can vary dramatically, and are critically dependent on pore geometry. Our study provides design guidelines for creating graphene nanopores with specific transport properties to meet the needs of diverse applications and for developing sensitive biological/chemical sensors with required performance characteristics.
    Keywords: ATK; Application; graphene nanopores; sensor; DNA;
    Area: graphene
    BibTeX:
    @article{Qiu2014,
      author = {Qiu, Wanzhi and Nguyen, Phuong and Skafidas, Efstratios},
      title = {Graphene nanopores: electronic transport properties and design methodology},
      journal = {Phys. Chem. Chem. Phys.},
      publisher = {The Royal Society of Chemistry},
      year = {2014},
      volume = {16},
      number = {4},
      pages = {1451--1459},
      doi = {http://dx.doi.org/10.1039/C3CP53777C}
    }
    
    Wen kai Zhao, Guo min Ji & De sheng Liu Contact position and width effect of graphene electrode on the electronic transport properties of dehydrobenzoannulenne molecule under bias 2014 Physics Letters A
    Vol. 378(4), 446-452 
    DOI  
    Abstract: By applying nonequilibrium Green's function formalism in combination with density functional theory, we have investigated the electronic transport properties of dehydrobenzoannulenne molecule attached to different positions of the zigzag graphene nanoribbons (ZGNRs) electrode. The different contact positions are found to drastically turn the transport properties of these systems. The negative differential resistance (NDR) effect can be found when the ZGNRs electrodes are mirror symmetry under the xz midplane, and the mechanism of NDR has been explained. Moreover, parity limitation tunneling effect can be found in a certain symmetry two-probe system and it can completely destroy electron tunneling process. The present findings might be useful for the application of ZGNRs-based molecular devices.
    Keywords: ATK, Application, electronic transport, zigzag graphene nanoribbon, dehydrobenzoannulenne, density functional theory, non-equilibrium Green's function
    Area: graphene
    BibTeX:
    @article{Zhao2014,
      author = {Zhao, Wen-kai and Ji, Guo-min and Liu, De-sheng},
      title = {Contact position and width effect of graphene electrode on the electronic transport properties of dehydrobenzoannulenne molecule under bias},
      journal = {Physics Letters A},
      year = {2014},
      volume = {378},
      number = {4},
      pages = {446--452},
      doi = {http://dx.doi.org/10.1016/j.physleta.2013.12.006}
    }
    
    Brahim Akdim, Ruth Pachter, Steve S. Kim, Rajesh R. Naik, Tiffany R. Walsh, Steven Trohalaki, Gongyi Hong, Zhifeng Kuang & Barry L. Farmer Electronic Properties of a Graphene Device with Peptide Adsorption: Insight from Simulation 2013 ACS Appl. Mater. Interfaces
    Vol. 5(15)ACS Applied Materials & Interfaces, 7470-7477 
    DOI  
    Abstract: In this work, to explain doping behavior of single-layer graphene upon HSSYWYAFNNKT (P1) and HSSAAAAFNNKT (P1-3A) adsorption in field-effect transistors (GFETs), we applied a combined computational approach, whereby peptide adsorption was modeled by molecular dynamics simulations, and the lowest energy configuration was confirmed by density functional theory calculations. On the basis of the resulting structures of the hybrid materials, electronic structure and transport calculations were investigated. We demonstrate that pi-pi stacking of the aromatic residues and proximate peptide backbone to the graphene surface in P1 have a role in the p-doping. These results are consistent with our experimental observation of the GFET's p-doping even after a 24-h annealing procedure. Upon substitution of three of the aromatic residues to Ala in (P1-3A), a considerable decrease from p-doping is observed experimentally, demonstrating n-doping as compared to the nonadsorbed device, yet not explained based on the atomistic MD simulation structures. To gain a qualitative understanding of P1-3A's adsorption over a longer simulation time, which may differ from aromatic amino acid residues' swift anchoring on the surface, we analyzed equilibrated coarse-grain simulations performed for 500 ns. Desorption of the Ala residues from the surface was shown computationally, which could in turn affect charge transfer, yet a full explanation of the mechanism of n-doping will require elucidation of differences between various aromatic residues as dependent on peptide composition, and inclusion of effects of the substrate and environment, to be considered in future work.
    Keywords: ATK-SE; Application; graphene; molecular adsorption; molecular dynamics; doping; peptides; distributed multipole analysis; molecular-dynamics; layer graphene; binding; field; transistors; parameters; scattering; proteins; accurate
    Area: graphene
    BibTeX:
    @article{Akdim2013,
      author = {Akdim, Brahim and Pachter, Ruth and Kim, Steve S. and Naik, Rajesh R. and Walsh, Tiffany R. and Trohalaki, Steven and Hong, Gongyi and Kuang, Zhifeng and Farmer, Barry L.},
      title = {Electronic Properties of a Graphene Device with Peptide Adsorption: Insight from Simulation},
      booktitle = {ACS Applied Materials & Interfaces},
      journal = {ACS Appl. Mater. Interfaces},
      publisher = {American Chemical Society},
      year = {2013},
      volume = {5},
      number = {15},
      pages = {7470--7477},
      doi = {http://dx.doi.org/10.1021/am401731c}
    }
    
    S Barzilai, F Tavazza & L E Levine Ab initio study of the mechanical and transport properties of pure and contaminated silver nanowires 2013 Journal of Physics: Condensed Matter
    Vol. 25(32), 325303 
    DOI  
    Abstract: The mechanical properties and conductance of contaminated and pure silver nanowires were studied using density functional theory (DFT) calculations. Several nanowires containing O 2 on their surfaces were elongated along two different directions. All of the NWs thinned down to single atom chains. In most simulations, the breaking force was not affected by the presence of the O 2 , and similar fracture strengths of ~1 nN were computed for the pure and impure NWs. When the O 2 became incorporated in the single atom chain, the fracture occurred at the Ag-O bond and a lower fracture strength was found. All of the simulations showed that the impurity interacted with the silver atoms to reduce the electron density in its nearby vicinity. A variety of conductance effects were observed depending on the location of the impurity. When the impurity migrated during the elongation to the thinnest part of the NW, it reduced the conductance significantly, and an ~1 G0 conductance (usually associated with a single atom chain) was calculated for three- and two-dimensional structures. When the impurity was adjacent to the single atom chain, the conductance reduced almost to zero. However, when it stayed far from the thinnest part of the NW, the impurity had only a small influence on the conductance.
    Keywords: ATK-SE; Application; nanowires; failure; mechanical properties; deformation; gold nanowires; geometry optimization; conductance; impurities; molecules
    Area: nanowires
    BibTeX:
    @article{Barzilai2013c,
      author = {Barzilai, S and Tavazza, F and Levine, L E},
      title = {Ab initio study of the mechanical and transport properties of pure and contaminated silver nanowires},
      journal = {Journal of Physics: Condensed Matter},
      year = {2013},
      volume = {25},
      number = {32},
      pages = {325303},
      doi = {http://dx.doi.org/10.1088/0953-8984/25/32/325303}
    }
    
    Yao-Jun Dong, Xue-Feng Wang, Ming-Xing Zhai, Jian-Chun Wu, Liping Zhou, Qin Han & Xue-Mei Wu Effects of Geometry and Symmetry on Electron Transport through Graphene-Carbon-Chain Junctions 2013 J. Phys. Chem. C
    Vol. 117(37)The Journal of Physical Chemistry C, 18845-18850 
    DOI  
    Abstract: The electron transport between two zigzag graphene nanoribbons (ZGNRs) connected by carbon atomic chains has been investigated by the nonequilibrium Green's function method combined with the density functional theory. The symmetry of the orbitals in the carbon chain critically selects the modes and energies of the transporting electrons. The electron transport near the Fermi energy can be well-manipulated by the position and the number of carbon chains contacting the nanoribbons. In symmetric ZGNRs connected by a central carbon chain, a square conductance step appears at the Fermi energy because the antisymmetric modes below it are not allowed to go through the chain. These modes can additionally contribute to the conductance if side carbon chains are added in the connection. By choosing a proper geometry configuration, we can realize Ohmic contact, current stabilizer, or the negative differential resistance phenomenon in the devices.
    Keywords: ATK; Application; graphene
    Area: graphene
    BibTeX:
    @article{Dong2013,
      author = {Dong, Yao-Jun and Wang, Xue-Feng and Zhai, Ming-Xing and Wu, Jian-Chun and Zhou, Liping and Han, Qin and Wu, Xue-Mei},
      title = {Effects of Geometry and Symmetry on Electron Transport through Graphene-Carbon-Chain Junctions},
      booktitle = {The Journal of Physical Chemistry C},
      journal = {J. Phys. Chem. C},
      publisher = {American Chemical Society},
      year = {2013},
      volume = {117},
      number = {37},
      pages = {18845--18850},
      doi = {http://dx.doi.org/10.1021/jp405318b}
    }
    
    Nahashon Ndegwa Gathitu, Yingfei Chang & Jingping Zhang Anchor position and donor/acceptor effects on transport properties in fused benzene-substituted oligothiophene molecular device 2013 Physica E: Low-dimensional Systems and Nanostructures
    Vol. 54(0), 247-252 
    DOI  
    Abstract: Utilizing non-equilibrium Green's functions in combination with density-functional theory, the transport properties of molecular devices based on fused benzene-substituted oligothiophenes were explored theoretically. The results show that the positions of anchor group and push-pull substituent groups can affect the conduction properties significantly, and the favorite current direction of the investigated devices can be tuned by applied bias. The first-principle calculations demonstrate that the forward current is favorable under low bias due to the asymmetric shift of transmission peaks of those that are derived from the resonant tunneling through HOMO state, while the asymmetric localization of HOMO states under high bias is beneficial to the reverse current.
    Keywords: ATK; Application; transport property; oligothiophene; molecular device; non-equilibrium Green's function; density-functional theory; negative differential resistance (NDR); ab-initio; junctions; circuits; formula; density
    Area: molecular electronics
    BibTeX:
    @article{Gathitu2013,
      author = {Gathitu, Nahashon Ndegwa and Chang, Yingfei and Zhang, Jingping},
      title = {Anchor position and donor/acceptor effects on transport properties in fused benzene-substituted oligothiophene molecular device},
      journal = {Physica E: Low-dimensional Systems and Nanostructures},
      year = {2013},
      volume = {54},
      number = {0},
      pages = {247--252},
      doi = {http://dx.doi.org/10.1016/j.physe.2013.06.032}
    }
    
    R.K. Ghosh & S. Mahapatra Proposal for Graphene-Boron Nitride Heterobilayer-Based Tunnel FET 2013 Nanotechnology, IEEE Transactions on
    Vol. 12(5)Nanotechnology, IEEE Transactions on, 665-667 
    DOI  
    Abstract: We investigate the gate-controlled direct band-to-band tunneling (BTBT) current in a graphene-boron nitride (G-BN) heterobilayer channel-based tunnel field effect transistor. We first study the imaginary band structure of hexagonal and Bernal-stacked heterobilayers by density functional theory, which is then used to evaluate the gate-controlled current under the Wentzel-Kramers-Brillouin approximation. It is shown that the direct BTBT is probable for a certain interlayer spacing of the G-BN which depends on the stacking orders.
    Keywords: ATK; Application; III-V semiconductors, band structure, boron compounds, density functional theory, field effect transistors, graphene, stacking, tunnel transistors, wide band gap semiconductors, BTBT current, Bernal-stacked heterobilayers, C-BN, Wentzel-Kramers-Brillouin approximation, density functional theory, gate-controlled direct band-to-band tunneling current, graphene-boron nitride heterobilayer-based tunnel FET, hexagonal heterobilayers, imaginary band structure, interlayer spacing, stacking orders, tunnel field effect transistor, Graphene, Logic gates, Materials, Photonic band gap, Stacking, Transistors, Tunneling, Band-to-band tunneling, complex band structure, graphene, tunnel field effect transistor (TFET)
    Area: graphene
    BibTeX:
    @article{Ghosh2013b,
      author = {Ghosh, R.K. and Mahapatra, S.},
      title = {Proposal for Graphene-Boron Nitride Heterobilayer-Based Tunnel FET},
      booktitle = {Nanotechnology, IEEE Transactions on},
      journal = {Nanotechnology, IEEE Transactions on},
      year = {2013},
      volume = {12},
      number = {5},
      pages = {665--667},
      doi = {http://dx.doi.org/10.1109/TNANO.2013.2272739}
    }
    
    Yan-Dong Guo, Xiao-Hong Yan & Yang Xiao Conformational change-induced switching behavior in pure-carbon systems 2013 RSC Advances
    Vol. 3(37), 16672-16680 
    DOI  
    Abstract: Based on first-principles calculation, the electronic transport properties of two-one-two dimensional carbon structures, graphene(benzene)-chain-graphene(benzene), are investigated. Switching behavior induced by conformational changes is observed, even for the systems with curved and quite long carbon chains. The spatial asymmetry of transmission channels between one- and two-dimensional carbon structures is found to be the physical mechanism behind this behavior, and it can be extended to metal systems. It is also found that the orientation of a transmission channel is able to be rotated by a nanotube (or curved graphene) through the non-planar pi-conjugated orbitals to modulate the switching behavior. Based on these structures, a kind of extremely-small pure-carbon logic operators and some other devices are proposed. As atomic motion could process information directly, the switching behavior and those devices would be very useful in nanomechanics.
    Keywords: ATK; Application; graphene; conformation;
    Area: graphene
    BibTeX:
    @article{Guo2013a,
      author = {Guo, Yan-Dong and Yan, Xiao-Hong and Xiao, Yang},
      title = {Conformational change-induced switching behavior in pure-carbon systems},
      journal = {RSC Advances},
      publisher = {The Royal Society of Chemistry},
      year = {2013},
      volume = {3},
      number = {37},
      pages = {16672--16680},
      doi = {http://dx.doi.org/10.1039/C3RA41401A}
    }
    
    Rupan Preet Kaur, Ravinder Singh Sawhney, Harpinder Kaur & Ramanjyot Kaur Length-Dependant Tunneling And Hopping Mechanism In Molecular Wires 2013 International Journal of Engineering Research & Technology (IJERT)
    Vol. 2(7), 394- 
    URL 
    Abstract: The temperature-dependant electron transport characteristics of three molecular wires of different molecular lengths belonging to the family of conjugated benzene molecules were studied. In this article, the conductance values for three molecular wires consisting of different number of benzene rings and amounting to different lengths at different temperature were calculated. The percentage change in conductance values were plotted with respect to temperature for each molecular wire in this research work. We concluded that the longest molecular wire of benzene having molecular length of 17.055 Å showed the most pronounced effect of temperature on conductance, even though this value was much smaller than the value exhibited by shortest molecular wire of length 5.003 Å. The results demonstrated that the shorter wires showed highly length dependence and temperature invariant conductance, whereas the longest wire exhibited weak length dependant and temperature variant behaviour. This electron transport behaviour was observed to be changing from tunnelling in shorter length wires to the hopping in longer length wires.
    Keywords: ATK; Application; Mesoscopic Systems, Resonant Tunneling, Thermionic emission, Hopping, Coulomb blockade.
    Area: molecular electronics
    BibTeX:
    @article{Kaur2013,
      author = {Rupan Preet Kaur and Ravinder Singh Sawhney and Harpinder Kaur and Ramanjyot Kaur},
      title = {Length-Dependant Tunneling And Hopping Mechanism In Molecular Wires},
      journal = {International Journal of Engineering Research & Technology (IJERT)},
      year = {2013},
      volume = {2},
      number = {7},
      pages = {394-},
      url = {http://www.ijert.org/browse/volume-2-2013/july-2013-edition?start=50}
    }
    
    Kavita Rao Khaddeo, Anurag Srivastava & Rajnish Kurchania Electronic Properties of GaN Nanotube: Ab Initio Study 2013 Journal of Computational and Theoretical Nanoscience
    Vol. 10(9), 2066-2070 
    DOI  
    Abstract: The electronic properties of single wall (graphitic) zigzag GaN nanotubes (GaNNTs) (n, 0) (n = 3-15) with tube diameter (d_t) ranging from 3.225 Å to 16.126 Å have been analyzed using ab-initio approach. The Density Functional Theory (DFT), with LDA-PZ and GGA-PBE as exchange-correlation functional, is employed to optimize the configuration and to evaluate the band structure of GaNNT with specified tube diameter (d_t) and chirality. The computation finds that at d_t = 3.23 Å, LDA and GGA shows almost same bandgap, whereas at d_t = 13.97 Å LDA shows metallic behavior and with GGA semiconducting. Noticeable, buckling has also been seen at d_t = 11.825 Å, which increases as radius of nanotube increases. In another finding, GaNNT of single atomic layer shows smaller band gap in comparison to that of multi atomic layer and this variation has been explained in terms of presence or absences of inter layer interactions. Interestingly, the GaNNT of single atomic layer does not show monotonic, semiconducting or metallic behavior within diameter ranging from 3.225 Å to 16.126 Å.
    Keywords: ATK; Application; ab-initio, band structure, buckling, electronic properties, zigzag GaN nanotube
    Area: nanotubes
    BibTeX:
    @article{Khaddeo2013,
      author = {Khaddeo, Kavita Rao and Srivastava, Anurag and Kurchania, Rajnish},
      title = {Electronic Properties of GaN Nanotube: Ab Initio Study},
      journal = {Journal of Computational and Theoretical Nanoscience},
      year = {2013},
      volume = {10},
      number = {9},
      pages = {2066--2070},
      doi = {http://dx.doi.org/10.1166/jctn.2013.3169}
    }
    
    Ahmed Mahmoud & Paolo Lugli Study on molecular devices with negative differential resistance 2013 Applied Physics Letters
    Vol. 103(3), 033506 
    DOI  
    Abstract: This paper provides a first-principles study for the transport behavior of molecular devices exhibiting wide bias range of negative differential resistance (NDR). The devices are composed of a diphenyl-dimethyl connected to carbon chains from each side, which are then linked to gold electrodes through thiol-gold bond. The devices show an odd/even oscillating behavior: the NDR appears only for "odd" numbers of carbon atoms in the chain. We look at different device parameters in order to determine the sources of the NDR behavior. We attribute this behavior to a lack of electrons within the chain in case of "odd" number of carbon atoms.
    Keywords: ATK-SE; Application; molecular electronics; negative differential resistance; NDR;
    Area: molecular electronics
    BibTeX:
    @article{Mahmoud2013,
      author = {Mahmoud, Ahmed and Lugli, Paolo},
      title = {Study on molecular devices with negative differential resistance},
      journal = {Applied Physics Letters},
      year = {2013},
      volume = {103},
      number = {3},
      pages = {033506},
      doi = {http://dx.doi.org/10.1063/1.4813844}
    }
    
    A. Mahmoud & P. Lugli First-Principles Study of a Novel Molecular Rectifier 2013 Nanotechnology, IEEE Transactions on
    Vol. 12(5)Nanotechnology, IEEE Transactions on, 719-724 
    DOI  
    Abstract: Designing molecular structures to meet certain behavior has become an important step in the field of molecular electronics. Interestingly, linker groups between molecules and electrodes show a critical role in the characteristic of the molecular devices. In this theoretical paper, a molecular rectifier that offers rectification ratio of more than three orders of magnitude, while preserving high on-current, is designed. In addition, a thorough investigation and explanation for the quantum transport through the device is provided. The characterization developed in this paper establishes a tight relation between the transmission spectra and electrostatic potential profile of the molecular device on the one hand, and the understanding/prediction of the rectification behavior on the other hand.
    Keywords: ab initio calculations, molecular configurations, molecular electronics, rectification, rectifiers, electrostatic potential, first-principles method, linker groups, molecular devices, molecular electronics, molecular rectifier, molecular structures, quantum transport, rectification ratio, transmission spectra, Molecular devices, nonequilibrium Green's function (NEGF), oligo-phenylene vinylene (OPV), rectifiers; ATK-SE; Application
    Area: molecular electronics
    BibTeX:
    @article{Mahmoud2013a,
      author = {Mahmoud, A. and Lugli, P.},
      title = {First-Principles Study of a Novel Molecular Rectifier},
      booktitle = {Nanotechnology, IEEE Transactions on},
      journal = {Nanotechnology, IEEE Transactions on},
      year = {2013},
      volume = {12},
      number = {5},
      pages = {719--724},
      doi = {http://dx.doi.org/10.1109/TNANO.2013.2271453}
    }
    
    Tao Ouyang, Huaping Xiao, Yuee Xie, Xiaolin Wei, Yuanping Chen & Jianxin Zhong Thermoelectric properties of gamma-graphyne nanoribbons and nanojunctions 2013 Journal of Applied Physics
    Vol. 114(7), 073710 
    DOI  
    Abstract: Using the Nonequilibrium Green's function approach, we investigate the thermoelectric properties of gamma-graphyne nanostructures. Compared with the graphene nanoribbons (GNRs), gamma-graphyne nanoribbons (GYNRs) are found to possess superior thermoelectric performance. Its thermoelectric figure of merit ZT is about 3-13 times larger than that in the GNRs. Meanwhile, the results show that the thermoelectric efficiency of GYNRs decreases as the ribbon width increases, while it increases monotonically with temperature. For the gamma-graphyne nanojunctions (GYNJs), the value of ZT increases dramatically as the width discrepancy between the left and right leads becomes more obvious. This improvement is mainly originated from the fact that the enhanced thermopower and degraded thermal conductance (including the electron and phonon contributions) outweigh the reduction of electronic conductance. Moreover, it is found that the thermoelectric behavior of GYNJs also depends on the geometric shape, which is explained by analyzing the unique width distribution of phonon contributed thermal conductance of GYNRs. These findings qualify gamma-graphyne as a promising candidate for thermoelectric applications and provide useful guideline for enhancing the thermoelectric performance in experiment.
    Keywords: ATK, Application, graphyne, graphene, nanoribbons, thermoelectric effects, ZT
    Area: graphene; thermo
    BibTeX:
    @article{Ouyang2013,
      author = {Ouyang, Tao and Xiao, Huaping and Xie, Yuee and Wei, Xiaolin and Chen, Yuanping and Zhong, Jianxin},
      title = {Thermoelectric properties of gamma-graphyne nanoribbons and nanojunctions},
      journal = {Journal of Applied Physics},
      year = {2013},
      volume = {114},
      number = {7},
      pages = {073710},
      doi = {http://dx.doi.org/10.1063/1.4818616}
    }
    
    Sweta Parashar, Pankaj Srivastava & Manisha Pattanaik Electrode materials for biphenyl-based rectification devices 2013 Journal of Molecular Modeling
    Vol. 19(10)Journal of Molecular Modeling, 4467-4475 
    DOI  
    Abstract: An ab initio approach was utilized to explore the electronic transport properties of 4'-thiolate-biphenyl-4-dithiocarboxylate (TBDT) sandwiched between two electrodes made of various materials X (X=Cu, Ag, and Au). Analysis of current-voltage (I-V) characteristics, rectification performance, transmission functions, and the projected density of states (PDOS) under various external voltage biases showed that the transport properties of these constructed systems are markedly impacted by the choice of electrode materials. Further, Cu electrodes yield the best rectifying behavior, followed by Ag and then Au electrodes. Interestingly, the rectification effects can be tuned by changing the torsion angle between the two phenyl rings, as well as by stretching the contact distances between the end group and the electrodes. For Cu, the maximum rectifying ratio increases by 37 % as the contact distance changes from 1.7 Å to 1.9 Å. This is due to an increase in coupling strength asymmetry between the molecule and the electrodes. Our findings are compared with the results reported for other systems. The present calculations are helpful not only for predicting the optimal electrode material for practical applications but also for achieving better control over rectifying performance in molecular devices.
    Keywords: ATK, Application, Electrode materials, Rectification effects, Torsion angles, Stretching distances, First-principles calculations, molecular electronics
    Area: molecular electronics
    BibTeX:
    @article{Parashar2013a,
      author = {Parashar, Sweta and Srivastava, Pankaj and Pattanaik, Manisha},
      title = {Electrode materials for biphenyl-based rectification devices},
      booktitle = {Journal of Molecular Modeling},
      journal = {Journal of Molecular Modeling},
      publisher = {Springer Berlin Heidelberg},
      year = {2013},
      volume = {19},
      number = {10},
      pages = {4467-4475},
      doi = {http://dx.doi.org/10.1007/s00894-013-1938-1}
    }
    
    A. Srivastava, N. Saraf & A.K. Nagawat Conductance Analysis of Zigzag Carbon Nanotubes Under Stress: Ab-Initio Study 2013 Quantum Matter
    Vol. 2(5), 401-407 
    DOI  
    Abstract: In the present paper, an ab-initio study of zigzag single walled carbon nanotubes (CNTs), has been performed to systematically analyse the stress effects on the conductivity. The calculations were made by using Atomistix Tool-Kit Virtual Nano Lab based on density functional theory (DFT) in self-consistent manner using generalized gradient approximation (GGA) under Perdew Burke Ernzerhoff (PBE) as exchange correlation functional. GGA based study confirms that on applying stress the conductivity of nanotubes dynamically changes as either semiconducting or metallic.
    Keywords: ATK; Application; nanotube; stress-strain; mechanical properties
    Area: nanotubes
    BibTeX:
    @article{Srivastava2013d,
      author = {A. Srivastava and N. Saraf and A. K. Nagawat},
      title = {Conductance Analysis of Zigzag Carbon Nanotubes Under Stress: Ab-Initio Study},
      journal = {Quantum Matter},
      year = {2013},
      volume = {2},
      number = {5},
      pages = {401-407},
      doi = {http://dx.doi.org/10.1166/qm.2013.1071}
    }
    
    W. Tian, Y.C. Zeng & Z.H. Zhang Electronic properties of graphene nanoribbons with periodically hexagonal nanoholes 2013 Journal of Applied Physics
    Vol. 114(7), 074307 
    DOI  
    Abstract: By using the first-principles method based on the density-functional theory, electronic properties of graphene nanoribbons punched with periodic nanoholes (GNRPNHs) are studied systematically. It has been shown that the zigzag-edge GNRPNH at the nonmagnetic state is always metal regardless of neck widths, but its metallic properties is obviously weakened due to nanohole effects, and at the anti-ferromagnetic states, its spin degeneracy still remains and the energy gap has only a smaller change. While for armchair-edge GNRPNHs, the situations are complicated. As compared with the perfect AGNRs, their band gaps become smaller or larger depending on the ribbon widths satisfying W=3p+1, 3p, or 3p-1. The analysis in depth shows that underlying origins are closely related to the width and edge shape (zigzag or armchair) of the neck subprime nanoribbon and edge subprime nanoribbon, which leads to the different quantum confinement effect. And also shown is the phenomenon of the odd-even oscillation for the band gap with the change of the neck width. These findings presented here provide theoretical references for experimentally punching desirable periodic nanoholes on the graphene nanoribbons to meet the special characteristics requirements of nanodevices.
    Keywords: ATK; Application; graphene nanoribbon
    Area: graphene
    BibTeX:
    @article{Tian2013,
      author = {Tian, W. and Zeng, Y. C. and Zhang, Z. H.},
      title = {Electronic properties of graphene nanoribbons with periodically hexagonal nanoholes},
      journal = {Journal of Applied Physics},
      year = {2013},
      volume = {114},
      number = {7},
      pages = {074307},
      doi = {http://dx.doi.org/10.1063/1.4818615}
    }
    
    Shyam Trivedi, Anurag Srivastava & Rajnish Kurchania Silicene and Germanene: A First Principle Study of Electronic Structure and Effect of Hydrogenation-Passivation 2014 Journal of Computational and Theoretical Nanoscience
    Vol. 11(3), 781-788 
    DOI  
    Abstract: Using first principle calculations we have explored the structural and electronic properties of silicene (silicon analogue of graphene) and germanene (germanium analogue of graphene). The structural optimization reveals that buckled silicene and germanene are more stable than their planar counter-parts by about 0.1 and 0.35 eV respectively. In comparison to planar graphene (buckling parameter Delta = 0 Å) the germanium sheet is buckled by 0.737 Å and silicene by 0.537 Å but both have similar electronic structure with zero band gap at K point as that of graphene. Further we investigated the effects of complete hydrogenation on these materials by considering different geometrical configurations (chair, boat, table and stirrup) and found that chair-like structure has the highest binding energy per atom in comparison to other structures. Hydrogenated silicene (silicane) shows an indirect band gap of 2.23 eV while hydrogenated germanene (germanane) possess a direct band gap of 1.8 eV.
    Keywords: ATK; Application; germanene; silicene; hydrogenation; first principle; electronic structure; binding energy
    Area: 2dmat
    BibTeX:
    @article{Trivedi2014a,
      author = {Trivedi, Shyam and Srivastava, Anurag and Kurchania, Rajnish},
      title = {Silicene and Germanene: A First Principle Study of Electronic Structure and Effect of Hydrogenation-Passivation},
      journal = {Journal of Computational and Theoretical Nanoscience},
      year = {2014},
      volume = {11},
      number = {3},
      pages = {781--788},
      doi = {http://dx.doi.org/10.1166/jctn.2014.3428}
    }
    
    Chengyu Yang & Quanfang Chen Electric resistance of carbon nanotube with a Cu chain: A first-principle calculation 2013 Proceedings of the Institution of Mechanical Engineers, Part N: Journal of Nanoengineering and Nanosystems
    Vol. 227(3), 115-119 
    DOI  
    Abstract: The electric resistance and transport properties of a carbon nanotube (5,5) adsorbed with a copper chain connected with two copper electrodes have been calculated by employing nonequilibrium Green's functions and Density Functional Theory. The properties of the pure carbon nanotube (5,5) with the Cu junction electrodes have also been calculated as a reference. Both the equilibrium and nonequilibrium conditions have been investigated. The results show that the resistance of the metallic carbon nanotube (5,5) has been reduced by the adsorption of a Cu chain due to the interaction between the Cu and the carbon nanotube. The change of the current-voltage curve slope is also explained in terms of transmission spectrum.
    Keywords: ATK, Application, nanotube, adsorption
    Area: nanotubes
    BibTeX:
    @article{Yang2013a,
      author = {Yang, Chengyu and Chen, Quanfang},
      title = {Electric resistance of carbon nanotube with a Cu chain: A first-principle calculation},
      journal = {Proceedings of the Institution of Mechanical Engineers, Part N: Journal of Nanoengineering and Nanosystems},
      year = {2013},
      volume = {227},
      number = {3},
      pages = {115--119},
      doi = {http://dx.doi.org/10.1177/1740349913483127}
    }
    
    G.L. Zhang, L. Pei, J. Yu, Y. Shang, H. Zhang & B. Liu Transport properties of nanowires with alternating organosilanylene and oligoethenylene units 2013 Theoretical Chemistry Accounts
    Vol. 132(9)Theoretical Chemistry Accounts, 1-7 
    DOI  
    Abstract: Transport properties of a series of sigma-pi-conjugated nanowires nSix(C=C)y (x = 2-4, y = 1-4, and n = 2-4) were studied by using non-equilibrium Green's function formalism with density functional theory. It is found that the silanylene moiety length, the ethenylene moiety length, and the whole molecular length play important roles in governing the transport properties of the nanowires: (1) the conductivity tends to be decreased with increasing the silanylene moiety length x; (2) lengthening the ethenylene moiety y is not always favorable to enhancing the conductivity; (3) the zero-bias conductance is decayed exponentially with the whole molecular length n. Further analysis indicates that the conductivities correlate well with the transmission spectra and the topology of the HOMO and LUMO states.
    Keywords: ATK; Application; theoretical study; transport property; silanylene; ethenylene; molecular electronics; polymeric organosilicon systems; negative differential resistance; ring-opening polymerization; conducting properties; molecular wires; emission spectra; silicon nanowire; radical ions; copolymers; efficient
    Area: molecular electronics; nanowires
    BibTeX:
    @article{Zhang2013b,
      author = {Zhang, G.L. and Pei, L. and Yu, J. and Shang, Y. and Zhang, H. and Liu, B.},
      title = {Transport properties of nanowires with alternating organosilanylene and oligoethenylene units},
      booktitle = {Theoretical Chemistry Accounts},
      journal = {Theoretical Chemistry Accounts},
      publisher = {Springer Berlin Heidelberg},
      year = {2013},
      volume = {132},
      number = {9},
      pages = {1-7},
      doi = {http://dx.doi.org/10.1007/s00214-013-1386-0}
    }
    
    Genghong Zhang, Yue Zheng & Biao Wang Dissimilar-electrodes-induced asymmetric characteristic and diode effect of current transport in zinc oxide tunnel junctions 2013 Journal of Applied Physics
    Vol. 114(4), 044111 
    DOI  
    Abstract: Based on the first principles simulations and quantum transport calculations, effects of dissimilar electrodes and interfaces on the current transport and relevant electrical properties in ZnO tunnel junctions as well as the mechanism of current asymmetric characteristic adjustment have been investigated. Our results show that the potential energy, built-in electric field, electron transmission probability, current, etc. in ZnO tunnel junctions can be tailored by adopting asymmetric electrode combinations. By adopting dissimilar electrodes to fabricate different potential barriers, we have performed manipulations on current transport in ZnO tunnel junctions and realized the enhancement and even the reversal of the current asymmetric characteristic. We also demonstrate that it is the different potential energy levels of the dissimilar electrodes in asymmetric tunnel junctions playing an important role in the adjustment of current asymmetry, which is innovative and different from the mechanism of current asymmetry adjustment through strain-induced piezopotential reversal. This investigation exhibits a novel and significant method for controlling or modifying the performances of electronic devices by utilizing dissimilar electrodes.
    Keywords: ATK; Application; tunnel diodes; ZnO; interfaces; tunneling junctions; work function;
    Area: interfaces; semi
    BibTeX:
    @article{Zhang2013c,
      author = {Zhang, Genghong and Zheng, Yue and Wang, Biao},
      title = {Dissimilar-electrodes-induced asymmetric characteristic and diode effect of current transport in zinc oxide tunnel junctions},
      journal = {Journal of Applied Physics},
      year = {2013},
      volume = {114},
      number = {4},
      pages = {044111},
      doi = {http://dx.doi.org/10.1063/1.4816796}
    }
    
    Sicong Zhu, Huahua Fu, Guoying Gao, Shuling Wang, Yun Ni & Kailun Yao A first principles study of novel one-dimensional organic half-metal vanadium-cyclooctatetraene wire 2013 The Journal of Chemical Physics
    Vol. 139(2), 024309 
    DOI  
    Abstract: The structural, electronic, and magnetic properties of one-dimensional vanadium-cyclooctatetraene[(V-COT)]-n wire and sandwich clusters are investigated by means of density functional theory. It is found that the (V-COT)-n SMW is half-metallic. Through the spin transportation calculations, the system for V-COT clusters coupled to gold electrodes performs nearly perfect spin filters. In addition, the I-V curve shows obviously negative differential resistance effects. These results suggest the potential applications of (V-COT)-n in spintronics.
    Keywords: ATK; Application; spin polarised transport; nanowire; organometallic compounds
    Area: nanowires; spin
    BibTeX:
    @article{Zhu2013b,
      author = {Zhu, Sicong and Fu, Huahua and Gao, Guoying and Wang, Shuling and Ni, Yun and Yao, Kailun},
      title = {A first principles study of novel one-dimensional organic half-metal vanadium-cyclooctatetraene wire},
      journal = {The Journal of Chemical Physics},
      year = {2013},
      volume = {139},
      number = {2},
      pages = {024309},
      doi = {http://dx.doi.org/10.1063/1.4813406}
    }
    
    Lin Zhu, Meichun Qian & Shiv N. Khanna Unusually large spin polarization and magnetoresistance in a FeMg8-FeMg8 superatomic dimer 2013 The Journal of Chemical Physics
    Vol. 139(6), 064306 
    DOI  
    Abstract: Electronic transport across a FeMg8 magnetic superatom and its dimer has been investigated using a density functional theory combined with Keldysh nonequilibrium Green's-function formalism. For a single cluster, our studies for the cluster supported in various orientations on a Au(100) surface show that the transport is sensitive to the contact geometry. Investigations covering the cases where the axes of Mg square antiprism are 45 degrees, perpendicular, and parallel to the transport direction, show that the equilibrium conductance, transferred charge, and current polarizations can all change significantly with orientation. Our studies on the transport across a magnetic superatom dimer FeMg8-FeMg8 focus on the effect of electrode contact distance and the support. The calculated I-V curves show negative differential resistance behavior at larger electrode-cluster contact distances. Further, the equilibrium conductance in ferromagnetic state shows an unusually high spin polarization that is about 81.48% for specific contact distance, and a large magnetoresistance ratio exceeding 500% is also found. The results show that the superatom assemblies can provide unusual transport characteristics, and that the spin polarization and magnetoresistance can be controlled via the contact geometry.
    Keywords: ATK; Application; electrical contacts; dimer; spin; magnetoresistance; building-blocks; large systems; transport; clusters; states
    Area: molecular electronics; spin
    BibTeX:
    @article{Zhu2013c,
      author = {Zhu, Lin and Qian, Meichun and Khanna, Shiv N.},
      title = {Unusually large spin polarization and magnetoresistance in a FeMg8-FeMg8 superatomic dimer},
      journal = {The Journal of Chemical Physics},
      year = {2013},
      volume = {139},
      number = {6},
      pages = {064306},
      doi = {http://dx.doi.org/10.1063/1.4817335}
    }
    
    S. Barzilai, F. Tavazza & L.E. Levine Sensitivity of gold nano-conductors to common contaminations: ab initio results 2013 Journal of Materials Science
    Vol. 48(19)Journal of Materials Science, 6619-6624 
    DOI  
    Abstract: Gold nanowire chains are considered a good candidate for nanoelectronic devices because they exhibit remarkable structural and electrical properties. A previous study shows that the beryllium-terminated BeO (0001) surface may be a useful platform for supporting nano gold conductors, since it preserves the nano-wire configuration, does not restrict its conductivity, and even enhances it. However, the influence of contamination on the conductivity of such conductors is unknown. Here, ab initio simulations were performed to determine the effect of commonly adsorbed contaminants (H2O and O2) on the conductivity of gold nano-conductors. We found that the presence of adsorbed impurities does not alter the good conductive ability of the conductors under examination.
    Keywords: ATK; Application; impurities; ballistic conductance; metallic nanowire;
    Area: nanowires
    BibTeX:
    @article{Barzilai2013b,
      author = {Barzilai, S. and Tavazza, F. and Levine, L.E.},
      title = {Sensitivity of gold nano-conductors to common contaminations: ab initio results},
      booktitle = {Journal of Materials Science},
      journal = {Journal of Materials Science},
      publisher = {Springer US},
      year = {2013},
      volume = {48},
      number = {19},
      pages = {6619-6624},
      doi = {http://dx.doi.org/10.1007/s10853-013-7460-0}
    }
    
    Yan-Dong Guo, Xiao-Hong Yan & Yang Xiao Electrical control of the spin polarization of a current in "pure-carbon" systems based on partially hydrogenated graphene nanoribbon 2013 Journal of Applied Physics
    Vol. 113(24), - 
    DOI  
    Abstract: Controlling a spin current by electrical means and eliminating the use of ferromagnetic contacts becomes a focus of research in spintronics, as compared with conventional magnetic control methods, electrical one could reduce the dimensions and energy consumption of integrated devices. Inspired by recent progress of controlling the hydrogenation on graphene [Xie et al., Appl. Phys. Lett. 98, 193113 (2011)], we investigate the electronic structure and spin-current transport of partially hydrogenated zigzag graphene nanoribbon (ZGNR) with various hydrogenation geometries, through first-principles calculations. It is found that for ZGNR in ferromagnetic edge-coupling state, near-edge hydrogenation would suppress the magnetization on the edge of ZGNR, and lower down the transmission around EF to zero except two peaks, which reside discretely on both sides of EF with opposite spins. Based on this feature, we propose and demonstrate a three-terminal device, where the spin polarization of the current can be modulated by gate voltage (Vg ) to vary from (almost) 100% to -100%, which could serve as a perfect electrically-controlled "pure-carbon" dual-spin filter. Especially, the spin polarization varies gradually with Vg , so a current with any ratio of spin-up to spin-down electron numbers can be achieved. Moreover, the influences of ZGNR width and hydrogenation-region length on the system's performance are also discussed and a large range of ZGNR configurations are found to be suitable for the application of such a device.
    Keywords: ATK; Application; graphene nanoribbon; hydrogenation; spin; device; electronics
    Area: graphene; spin
    BibTeX:
    @article{Guo2013,
      author = {Guo, Yan-Dong and Yan, Xiao-Hong and Xiao, Yang},
      title = {Electrical control of the spin polarization of a current in "pure-carbon" systems based on partially hydrogenated graphene nanoribbon},
      journal = {Journal of Applied Physics},
      year = {2013},
      volume = {113},
      number = {24},
      pages = {-},
      doi = {http://dx.doi.org/10.1063/1.4811716}
    }
    
    Mudassir M. Husain Transition from Carbon Nanoballs to Nanocapsules With Reference To Structural and Molecular Electronic Properties 2013 International Journal of Research in Engineering and Science
    Vol. 1(1), 36-47 
    URL 
    Abstract: We have investigated theoretically the variation in energetics and electronic properties during the gradual transition from spherical or nearly spherical form (as in case of armchair) to capsule formation. The zigzag and armchair configurations of carbon nanostructures with different length to diameter (l/d) ratio have been studied. Zigzag C80 and (9,0) single wall nanocapsules, armchair C70 and (5,5) carbon nanocapsules (Cncs) system have been theoretically investigated. We have used semi-empirical molecular orbital method, at the level of PM3 type quantum mechanical model. The geometry of these molecular systems has been suitably optimized. The parameters studied are various molecular properties, energy values, frontier orbital (HOMO and LUMO) energies, heats of formation, interfrontier energy gap (Eg), density of states (DOS), electron difference density (EDD) and electrostatic difference potential (EDP) of the capsules. The structures studied were found to be stable with a minimum energy band gap respectively of 3.73 and 4.66 eV, in case of zigzag and armchair configuration and exhibit insulating properties.
    Keywords: ATK; Application; Carbon nanocapsule, frontier orbitals, density of states (DOS), electron difference density (EDD), electrostatic difference potential (EDP)
    Area: fullerenes
    BibTeX:
    @article{Husain2013,
      author = {Mudassir M. Husain},
      title = {Transition from Carbon Nanoballs to Nanocapsules With Reference To Structural and Molecular Electronic Properties},
      journal = {International Journal of Research in Engineering and Science},
      year = {2013},
      volume = {1},
      number = {1},
      pages = {36-47},
      url = {http://ijres.org/v1i1.html}
    }
    
    Mudassir M. Husain Carbon Dioxide Adsorption on Single Walled Bamboo-Like Carbon Nanotubes (SWBCNT): A Computational Study 2013 International Journal of Research in Engineering and Science
    Vol. 1(2), 13-26 
    URL 
    Abstract: Adsorption of CO2 on single walled (12,0) and (5,5) bamboo-like carbon nanotubes (SWBCNT) has been investigated theoretically. Adsorption of CO2 at 12 different sites is calculated on the surface of these tubes. The advantage of using BCNTs is the multiple number of potential binding sites available near the partition wall. On them, CO2 can get adsorbed and the number is greater as compared to normal SWCNTs. It has been observed in BCNTs, that the CO2 molecule gets absorbed via chemisorption at most of the sites. The mechanism is that the molecule breaks and the oxygen atom binds to the carbon atom of BCNT surface, changing sp2 to sp3 hybrization. The adsorption has been interpreted with reference to change in structural and electronic properties e.g. length, diameter, bond length, charge transfer and energy band gap of tubes. Our findings show that the molecule is adsorbed more strongly with larger adsorption energy on (12,0) surface than on the (5,5). The calculated value of adsorption energy in the present work is greater than the values reported previously on SWCNTs. For the first time the adsorption of any gas has been carried out on SWBCNTs.
    Keywords: ATK; Application; Bamboo-like carbon nanotubes, CO2 , adsorption, physisorption, chemisorption
    Area: fullerenes
    BibTeX:
    @article{Husain2013a,
      author = {Mudassir M. Husain},
      title = {Carbon Dioxide Adsorption on Single Walled Bamboo-Like Carbon Nanotubes (SWBCNT): A Computational Study},
      journal = {International Journal of Research in Engineering and Science},
      year = {2013},
      volume = {1},
      number = {2},
      pages = {13-26},
      url = {http://ijres.org/v1i2.html}
    }
    
    Neeraj K. Jaiswal & Pankaj Srivastava Tailoring the Electronic Structure of Zigzag Graphene Nanoribbons via Cu Impurities 2013 Journal of Computational and Theoretical Nanoscience
    Vol. 10(6), 1441-1445 
    DOI  
    Abstract: We employed density functional theory based spin polarised calculations to explore the structural stability and electronic properties of ZGNR using Cu as a terminating element as well as a substitutional dopant at various sites. In both the cases (termination and doping) Cu impurities affect the electronic properties of nanoribbons in a different way. The calculated formation energy indicates that all the structures are energetically feasible except the both edges Cu-doped ribbons. Binding energy analysis confirms that Cu impurities are strongly bound to ZGNR in all considered configurations. Moreover, ribbon edge is regarded as the most feasible site for substitutional Cu atoms in ZGNR. The electronic properties of ZGNR are sensitive to the position of Cu atoms and the ribbon width. It is revealed that ZGNR can be made semiconducting, semi-metallic, half metallic or purely metallic in nature merely by changing the ribbon width or the position of Cu atoms. The predicted half metallicity for one edge Cu-terminated ZGNR is robust against the choice of exchange correlation potential.
    Keywords: ATK; Application; binding energy; electronic structure; formation energy; spin polarization
    Area: graphene; spin
    BibTeX:
    @article{Jaiswal2013,
      author = {Jaiswal, Neeraj K. and Srivastava, Pankaj},
      title = {Tailoring the Electronic Structure of Zigzag Graphene Nanoribbons via Cu Impurities},
      journal = {Journal of Computational and Theoretical Nanoscience},
      year = {2013},
      volume = {10},
      number = {6},
      pages = {1441--1445},
      doi = {http://dx.doi.org/10.1166/jctn.2013.2868}
    }
    
    Neeraj K. Jaiswal & Pankaj Srivastava Enhanced metallicity and spin polarization in zigzag graphene nanoribbons with Fe impurities 2013 Physica E: Low-dimensional Systems and Nanostructures
    Vol. 54(0), 103-108 
    DOI  
    Abstract: We present the first principles calculations of zigzag graphene nanoribbons (ZGNR), passivated and substitutionally doped with Fe atoms. The structural stability, electronic structures and transport properties have been discussed within the frame work of density functional theory. Present calculations revealed that ribbons with a single Fe impurity per unit cell exhibit magnetic ground state independent of the site of impurity atom. All the structures have stable binding and one-edge Fe-passivated ZGNR is the most stable configuration in contrast to other considered structures including the pristine one. The electronic properties are found sensitive to the impurity site rather than the GNR width. Our findings include the possibility of converting pristine ZGNR into highly conducting ribbons which can also sustain the spin polarized current. A high spin polarization (up to 95%) has been achieved which pledges for its potential application in spintronic devices.
    Keywords: ATK; Application; graphene nanoribbon, electronic structure, spin polarization, transmission spectra, I-V characteristics; half-metallicity; transport-properties; edge; field
    Area: graphene; spin
    BibTeX:
    @article{Jaiswal2013a,
      author = {Jaiswal, Neeraj K. and Srivastava, Pankaj},
      title = {Enhanced metallicity and spin polarization in zigzag graphene nanoribbons with Fe impurities},
      journal = {Physica E: Low-dimensional Systems and Nanostructures},
      year = {2013},
      volume = {54},
      number = {0},
      pages = {103--108},
      doi = {http://dx.doi.org/10.1016/j.physe.2013.06.002}
    }
    
    Ravinder Kumar, Kulbir Kaur, Vijay Lamba & Derick Engles Modeling the Conductivity Enhancement in Doped Single-walled Carbon Nanotube (SWCNT) 2013 International Journal of Scientific & Engineering Research
    Vol. 4(6), 2254 
    URL 
    Abstract: In this work we have modeled and simulated the electronic charge transport properties for a Single-walled Carbon Nano-tube with different geometries using first-principle calculations and Nonequilibrium Green's function (NEGF) method. We modeled a Single-walled Carbon Nano-tube by rolling Armchair (4,4) or Zigzag (4,0) Graphene Nanoribbon strips with the different doping atoms (S,N,P) using semi-empirical Extended Huckle Theory (EHT) within the framework of non-equilibrium green function (NEGF). The simulations were carried in Device mode using Atomistic Tool Kit (ATK-12.8.2) and its graphical interface (custom analyzer) Virtual Nano Lab till the self-consistent results was reached. The effect of the change in conductance and I-V characteristics of the junction was visualized for various transport parameters. The distinct changes in conductance reported as the positions , concentration and type of dopants was varied in central region of the CNT between two electrodes at different bias voltages from -2V to 2 V with steps of .50 V. This suggested conductance enhancement mechanism for the charge transport in the doped Single-walled Carbon Nano-tube at different positions is important for the design of CNT based nano electronic devices.
    Keywords: ATK-SE; Application; electronic charge transport; extended Huckel theory (EHT); NEGF; SWCNT; Dopants; GNRs
    Area: nanotubes
    BibTeX:
    @article{Kumar2013,
      author = {Ravinder Kumar and Kulbir Kaur and Vijay Lamba and Derick Engles},
      title = {Modeling the Conductivity Enhancement in Doped Single-walled Carbon Nanotube (SWCNT)},
      journal = {International Journal of Scientific & Engineering Research},
      year = {2013},
      volume = {4},
      number = {6},
      pages = {2254},
      url = {http://www.ijser.org/researchpaper/Modeling-the-Conductivity-Enhancement-in-Doped-Single--walled-Carbon-Nanotube-SWCNT.pdf}
    }
    
    Jian-Chang Li & Xing Gong Diode rectification and negative differential resistance of dipyrimidinyl-diphenyl molecular junctions 2013 Organic Electronics
    Vol. 14(10), 2451-2458 
    DOI  
    Abstract: Addressable Au/dipyrimidinyl-diphenyl/Au molecular junctions are fabricated using elastic polymer stamp-printing method. To study the charge transport, current-voltage measurements are carried out from 95 up to 295 K in vacuum under both dark and light conditions. Reversible diode rectification and negative differential resistance phenomena are observed. The rectification efficiency dramatically decreases upon temperature increase or light illumination. Theoretical calculations based on the non-equilibrium Greenäs function method combined with the density functional theory is performed to elucidate the negative differential resistance behaviors. We show that the different rectification efficiency is caused by the interfacial asymmetry and the dipole effects. The negative differential resistance may be attributed to the variation of the coupling degree between the incident states of the Au electrodes and the molecular orbitals, which depends largely on the S-Au contact geometry. The direct tunneling and Fowler-Nordheim tunneling act as the main transport mechanisms for low and high bias regions, respectively. The barrier height depends largely on the light illumination, substrate temperature, and bias polarity. The distinctly different adsorbing nature of the Au/molecule interface may account for the performances.
    Keywords: ATK; Application; metal/molecule/metal junction; diode rectification; optoelectronic switching; negative differential resistance; charge transport
    Area: molecular electronics
    BibTeX:
    @article{Li2013d,
      author = {Li, Jian-Chang and Gong, Xing},
      title = {Diode rectification and negative differential resistance of dipyrimidinyl-diphenyl molecular junctions},
      journal = {Organic Electronics},
      year = {2013},
      volume = {14},
      number = {10},
      pages = {2451--2458},
      doi = {http://dx.doi.org/10.1016/j.orgel.2013.06.014}
    }
    
    Sweta Parashar, Pankaj Srivastava & Manisha Pattanaik Modeling of Cu-linked rectification devices by varying torsion angles 2013 Journal of Computational Electronics
    Vol. 12(4)Journal of Computational Electronics, 775-781 
    DOI  
    Abstract: Using the nonequilibrium Green's function (NEGF) method in combination with the density functional theory (DFT), we have analyzed the rectifying performance in Cu-linked molecular devices by varying torsion angles (0-90 degrees). The linking effect of Cu atom has been investigated by calculating current-voltage (I-V) characteristics, rectification performance, transmission functions, projected density of states (PDOS), and molecular projected self-consistent Hamiltonian (MPSH). Present calculations revealed that linking of Cu in combination with conjugated dithiocarboxylate (-CS2) and standard thiol linkers significantly affects the metal-molecule coupling asymmetry, and thus the rectifying behavior in molecular devices. Further, the subsequent studies show that the left-right combination of -CS2 linker and Cu atom displays higher rectification ratio at various torsion angles in gold-biphenyl-gold junctions than thiol and Cu linkers. The calculated results are helpful not only in predicting an optimal combination of linking groups for realistic applications but also provide the way for better control of rectification effects in molecular devices.
    Keywords: ATK; Application; linking group effects; torsion angles; rectifying performance; first-principles; molecular electronics
    Area: molecular electronics
    BibTeX:
    @article{Parashar2013,
      author = {Parashar, Sweta and Srivastava, Pankaj and Pattanaik, Manisha},
      title = {Modeling of Cu-linked rectification devices by varying torsion angles},
      booktitle = {Journal of Computational Electronics},
      journal = {Journal of Computational Electronics},
      publisher = {Springer US},
      year = {2013},
      volume = {12},
      number = {4},
      pages = {775-781},
      doi = {http://dx.doi.org/10.1007/s10825-013-0482-7}
    }
    
    You Lin Peng, Yan Hong Zhou, Xiao Hui Qiu & Li Li Zhou The Role of the Electrode Size of to the Elecronic Transport Properties 2013 Applied Mechanics and Materials
    Vol. 320(5), 88-91 
    DOI  
    Abstract: We study the size effects of the electrode to the elecronic transport properties via a molecule of benzene sandwiched between two graphene electrodes using an ab initio nonequilibrium Green's function method and density function theory. More specially, two types of electrodes are selected: one ring wide electrodes and two rings wide electrodes. We find that the current cross the system that is with two rings wide electrodes is bigger than the current that is with one ring wide electrodes. Detailed analyses of the projected density of states and the transmission spectra of the system reveals the mechanism: with wider electrodes, transmission coeffients walk nearer to the fermi energy and may make contribution to the current at applied bias voltages.
    Keywords: ATK; Application; density functional theory; projected density of states; molecular electronics
    Area: molecular electronics
    BibTeX:
    @article{Peng2013,
      author = {You Lin Peng and Yan Hong Zhou and Xiao Hui Qiu and Li Li Zhou},
      title = {The Role of the Electrode Size of to the Elecronic Transport Properties},
      journal = {Applied Mechanics and Materials},
      year = {2013},
      volume = {320},
      number = {5},
      pages = {88-91},
      doi = {http://dx.doi.org/10.4028/www.scientific.net/AMM.320.88}
    }
    
    C.Q. Qu, C.Y. Wang, L. Qiao, S.S. Yu & H.B. Li Transport properties of chemically functionalized graphene nanoribbon 2013 Chemical Physics Letters
    Vol. 578(0), 97-101 
    DOI  
    Abstract: We perform a theoretical calculation in chemically functionalized zigzag graphene nanoribbons, which are terminated with different single atoms or groups, using density functional theory and nonequilibrium Green's function techniques. The calculation results reveal that these different species of atoms and groups have a significant impact on the edge states near Fermi level as well as the spin-dependent electronic transport properties. The calculated I-V curves exhibit negative differential resistance, which can be used for application in molecular spin electronic device.
    Keywords: ATK; Application; graphene nanoribbon; chemical functionalization; spin-polarized transport; negative differential resistance (NDR); room-temperature; molecular junctions; conductance device
    Area: graphene; spin
    BibTeX:
    @article{Qu2013,
      author = {Qu, C.Q. and Wang, C.Y. and Qiao, L. and Yu, S.S. and Li, H.B.},
      title = {Transport properties of chemically functionalized graphene nanoribbon},
      journal = {Chemical Physics Letters},
      year = {2013},
      volume = {578},
      number = {0},
      pages = {97--101},
      doi = {http://dx.doi.org/10.1016/j.cplett.2013.05.071}
    }
    
    S. Sivasathya & D. John Thiruvadigal The effects of defects on electron transport in metallic single wall carbon nanotubes 2013 Nanosystems: Physics, Chemistry, Mathematics
    Vol. 4(3), 405-408 
    URL 
    Abstract: We report the transport behavior of an openend metallic single wall carbon nanotube (SWCNT) with and without local structural defects using the nonequilibrium Green's functions approach together with the density functional theory (DFT). The transmission spectra and the projected density of states for the devices such as SWCNT (3, 3), (4, 4), (5, 5) and (6, 6) with and without defects were compared. In all cases, we found that the Stone-Wales defect had an almost negligible impact on the electrical performance compared to the monovacancy defect of the single wall carbon nanotubes at the Fermi level. The current-voltage (IV) characteristics of the devices were studied using the generalized Landauer-Buttiker formalism under low bias conditions. From our results, we concluded that our systems were suitable for use in various CNT based nanoelectronic devices.
    Keywords: ATK; Application; Stone-Wales defect; density functional theory; single wall carbon nanotubes; transport properties; I-V characteristics
    Area: nanotubes
    BibTeX:
    @article{Sivasathya2013,
      author = {S. Sivasathya and D. John Thiruvadigal},
      title = {The effects of defects on electron transport in metallic single wall carbon nanotubes},
      journal = {Nanosystems: Physics, Chemistry, Mathematics},
      year = {2013},
      volume = {4},
      number = {3},
      pages = {405-408},
      url = {http://nanojournal.ifmo.ru/en/articles-2/volume4/4-3/mam-12/paper15/}
    }
    
    Anurag Srivastava & Neha Tyagi Structural and Electronic Properties of AlAs Nanocrystal: Ab-Initio Study 2013 Journal of Computational and Theoretical Nanoscience
    Vol. 10(5), 1222-1230 
    DOI  
    Abstract: Structural stability and electronic properties of AlAs nanocrystal of different sizes ranging from 0.5 to 1.4 nm have been analyzed in its zincblende (B3), wurtzite (B4), NiAs (B8), rocksalt (B1) and CsCl (B2) type phases. The electronic structure of nanocrystal is modeled within the framework of density functional theory with Perdew-Zunger (PZ) parameterized local density approximation (LDA) and Perdew, Burke and Ernzerhof parameterized generalized gradient approximation (GGA). The lattice parameters, bulk modulus and pressure derivatives of nanocrystals at different sizes have been calculated for each stable phase. The computation shows that within the size range taken into consideration the B2 type phase at 0.72 nm possess the highest bulk modulus and can be considered as mechanically much stronger amongst all other nanocrystals. The study observes that the band gap of nanocrystal in its original B3 type phase increases as the size of the nanocrystal decreases from 1.4 nm to 0.74 nm whereas the same phase is metallic within the size range of 0.5 nm to 0.6 nm.
    Keywords: ATK; Application; ab initio; bulk modulus; electronic structure; nanocrystal; semiconductors
    Area: semi
    BibTeX:
    @article{Srivastava2013b,
      author = {Srivastava, Anurag and Tyagi, Neha},
      title = {Structural and Electronic Properties of AlAs Nanocrystal: Ab-Initio Study},
      journal = {Journal of Computational and Theoretical Nanoscience},
      year = {2013},
      volume = {10},
      number = {5},
      pages = {1222--1230},
      doi = {http://dx.doi.org/10.1166/jctn.2013.2832}
    }
    
    Anurag Srivastava, Neha Tyagi & Rajeev Ahuja First-principles study of structural and electronic properties of gallium based nanowires 2013 Solid State Sciences
    Vol. 23(0), 35-41 
    DOI  
    Abstract: Abstract Structural stability and electronic properties of GaX (X = N, P, As and Sb) nanowires have been investigated using first-principles based density function theory approach. Out of linear, zigzag, square and hexagon shaped configuration, the square shaped geometry is energetically most stable. The computation of lattice parameters, bulk modulus and pressure derivatives for these Ga based nanowires observes the highest bulk modulus for hexagonal shaped GaN nanowire amongst all, suggest the mechanical strength of this geometry. Electronic band structures analysis shows the semiconducting as well as metallic behavior of these nanowires.
    Keywords: ATK, Application, semiconductors, nanowires, electronic structure, first-principles calculation, bulk modulus, semiconductors; nanowires; electronic structure; first-principles calculation; bulk modulus
    Area: nanowires; semi
    BibTeX:
    @article{Srivastava2013c,
      author = {Srivastava, Anurag and Tyagi, Neha and Ahuja, Rajeev},
      title = {First-principles study of structural and electronic properties of gallium based nanowires},
      journal = {Solid State Sciences},
      year = {2013},
      volume = {23},
      number = {0},
      pages = {35--41},
      doi = {http://dx.doi.org/10.1016/j.solidstatesciences.2013.05.014}
    }
    
    Shyam Trivedi, Anurag Srivastava & Rajnish Kurchania Electronic and Transport Properties of Silicene Nanoribbons 2014 Journal of Computational and Theoretical Nanoscience
    Vol. 11(3), 789-794 
    DOI  
    Abstract: Using Density Functional Theory (DFT) and Local Density Approximation (LDA) functional we have explored the width dependent bandgap variation and transport properties of silicene nanoribbons (SNRs). Both the armchair and zigzag SNRs are cut from the semi-metallic buckled silicon sheet. Armchair SNRs are nonmagnetic and exhibit a three family bandgap decay profile with increasing width similar to Graphene nanoribbons (GNRs). In comparison to armchair SNRs, the influence of edge spin polarization is much greater on the zigzag SNRs. The anti-ferromagnetic state is the most stable ground state for zigzag ribbons showing monotonous decrease in band gap with increasing width. Quantum transport properties have been analysed by calculating the transmission spectra of different groups of armchair and zigzag SNRs. Our result shows that wider ribbons have large transmission values.
    Keywords: ATK; Application; silicene nanoribbon;
    Area: 2dmat
    BibTeX:
    @article{Trivedi2014,
      author = {Trivedi, Shyam and Srivastava, Anurag and Kurchania, Rajnish},
      title = {Electronic and Transport Properties of Silicene Nanoribbons},
      journal = {Journal of Computational and Theoretical Nanoscience},
      year = {2014},
      volume = {11},
      number = {3},
      pages = {789--794},
      doi = {http://dx.doi.org/10.1166/jctn.2014.3429}
    }
    
    Yuta Tsuji, Takayuki Semoto & Kazunari Yoshizawa A Bipodal Dicyano Anchor Unit for Single-Molecule Spintronic Devices 2013 ChemPhysChem
    Vol. 14(11), 2470-2475 
    DOI  
    Abstract: The conductance through single 7,7,8,8-tetracyanoquinodimethane (TCNQ) connected to gold electrodes is studied with the nonequilibrium Green's function method combined with density functional theory. The aim of the study is to derive the effect of a dicyano anchor group, =C(CN)2, on energy level alignment between the electrode Fermi level and a molecular energy level. The strong electron-withdrawing nature of the dicyano anchor group lowers the LUMO level of TCNQ, resulting in an extremely small energy barrier for electron injection. At zero bias, electron transfer from electrodes easily occurs and, as a consequence, the anion radical state of TCNQ with a magnetic moment is formed. The unpaired electron in the TCNQ anion radical causes an exchange splitting between the spin-alpha and spin-beta transmission spectra, allowing the single TCNQ junction to act as a spin-filtering device.
    Keywords: atk; application; adsorption; cyanides; density functional calculations; electron transport; molecular devices; molecular electronics; spintronics; negative differential resistance (NDR); electron-transport; charge transport; metal junctions; conductance; chemistry; radicals; sulfides; surfaces
    Area: molecular electronics; spin
    BibTeX:
    @article{Tsuji2013,
      author = {Tsuji, Yuta and Semoto, Takayuki and Yoshizawa, Kazunari},
      title = {A Bipodal Dicyano Anchor Unit for Single-Molecule Spintronic Devices},
      journal = {ChemPhysChem},
      publisher = {WILEY-VCH Verlag},
      year = {2013},
      volume = {14},
      number = {11},
      pages = {2470--2475},
      doi = {http://dx.doi.org/10.1002/cphc.201300136}
    }
    
    Li hua Wang, Zi zhen Zhang, Cun qin Lv, Bing jun Ding & Yong Guo Large negative differential resistance and rectifying performance modulated by contact sites in fused thiophene trimmer-based molecular devices 2013 Physics Letters A
    Vol. 377(31–33), 1920-1924 
    DOI  
    Abstract: Abstract By applying density functional theory with non-equilibrium Green's function formalism, we have carried out a theoretical study of the electron transport in fused thiophene trimmer-based molecular devices with ethylene connections at three different sites. The simulation results indicate that the electronic transport properties strongly depend on the contact sites. Negative differential resistance and rectifying behaviors occur simultaneously in the current-voltage curves when ethylene connects the fused thiophene trimer at one second-nearest site and one third-nearest site. A larger negative differential resistance occurs only when ethylene connects the fused thiophene trimer at two second-nearest sites.
    Keywords: ATK; Application; molecular device; density functional theory; non-equilibrium Green's function; negative differential resistance; current rectification; transport-properties; 1st-principles; junctions; rectification; conductance; derivatives; geometries; distance; wires
    Area: molecular electronics
    BibTeX:
    @article{Wang2013b,
      author = {Wang, Li-hua and Zhang, Zi-zhen and Lv, Cun-qin and Ding, Bing-jun and Guo, Yong},
      title = {Large negative differential resistance and rectifying performance modulated by contact sites in fused thiophene trimmer-based molecular devices},
      journal = {Physics Letters A},
      year = {2013},
      volume = {377},
      number = {31–33},
      pages = {1920--1924},
      doi = {http://dx.doi.org/10.1016/j.physleta.2013.05.034}
    }
    
    L. Zhu & K.L. Yao Spin transport and magnetic properties of a copper(II) coordination organometallic molecule 2013 Journal of Magnetism and Magnetic Materials
    Vol. 344(0), 14-19 
    DOI  
    Abstract: We study the effects of the characteristics of electrodes and electrode-molecule contacts on the spin-polarized transport properties of a dimeric CuII magnetic single-molecule [Cu2(L1)(hfac)2].·3CH3CN.H2O by density-functional theory (DFT) combined with the Keldysh nonequilibrium Green's-function (NEGF) formalism. It is found that the I-V curve shows negative differential resistance behavior due to the shifting of electrode band structure and the asymmetric coupling between the molecule and the electrodes under bias. In addition, the device presents integrated spintronic functionalities such as switch, spin valve and spin filter, associated with perfect negative magnetoresistance.
    Keywords: ATK; Application; multifunctional molecular device; spin-polarized transport; spintronics; NEGF
    Area: molecular electronics; spin
    BibTeX:
    @article{Zhu2013a,
      author = {Zhu, L. and Yao, K.L.},
      title = {Spin transport and magnetic properties of a copper(II) coordination organometallic molecule},
      journal = {Journal of Magnetism and Magnetic Materials},
      year = {2013},
      volume = {344},
      number = {0},
      pages = {14--19},
      doi = {http://dx.doi.org/10.1016/j.jmmm.2013.04.083}
    }
    
    Anders Blom & Kurt Stokbro Atomistic modeling of semiconductor interfaces 2013 Journal of Computational Electronics
    Vol. 12(4)Journal of Computational Electronics, 623-637 
    DOI  
    Abstract: A strong contributing factor to the success of silicon has been a parallel development of accurate modeling tools. For the efficient introduction of new device architectures at the nanoscale, it is necessary to develop similar tools that can handle all the relevant aspects of the new physical properties that will be utilized. This is a very challenging task, as we are dealing not only with many new materials and even more combinations of elements materials, but also effects due the small device sizes and even reduced dimensionality in the form of confinement. In this article we turn our attention to the topic of simulating interfaces from first principles, on the atomic scale. As device dimensions shrink, interfaces start to play a dominating role, and need to be treated as an active part of the device, and not just as an invisible boundary between different materials. We will review the theoretical framework for computing properties of single interfaces, and provide several examples of the types of simulations that can be performed. A concluding separate section is dedicated to computing band offsets.
    Keywords: ATK; Application; Interfaces; Electron transport; Tunneling; Density functional theory (DFT); Non-equilibrium Green's functions (NEGF); Band offset; Scattering; Transistor; review;
    Area: semi; interfaces
    BibTeX:
    @article{Blom2013,
      author = {Blom, Anders and Stokbro, Kurt},
      title = {Atomistic modeling of semiconductor interfaces},
      booktitle = {Journal of Computational Electronics},
      journal = {Journal of Computational Electronics},
      publisher = {Springer US},
      year = {2013},
      volume = {12},
      number = {4},
      pages = {623-637},
      doi = {http://dx.doi.org/10.1007/s10825-013-0531-2}
    }
    
    Teppei Kato, Shinji Usui & Takahiro Yamamoto Nanostructural Effects on Thermoelectric Power of Graphene Nanoribbons 2013 Japanese Journal of Applied Physics
    Vol. 52, 06GD05 
    DOI  
    Abstract: Nanostructural effects on the thermoelectric power of graphene nanoribbons (GNRs) are revealed through first-principles simulation based on the density functional theory combined with nonequilibrium Green's function theory. The thermoelectric power of GNRs exhibits essentially different behavior depending on their edge structure and ribbon width. For zigzag-edged GNRs, the thermoelectric power shows a peculiar energy dependence originating from edge-localized electronic states with energy near the Fermi level. On the other hand, for armchair-edged GNRs (AGNRs), the thermoelectric power is classified into three categories depending on the ribbon width. Among AGNRs with similar ribbon width, an AGNR belonging to a category satisfying mod(Na, 3)=1 displays the largest thermoelectric power, where Na is the integer determining the ribbon width of an AGNR.
    Keywords: ATK; Application; graphene nanoribbon; thermoelectric power
    Area: graphene; thermo
    BibTeX:
    @article{Kato2013,
      author = {Teppei Kato and Shinji Usui and Takahiro Yamamoto},
      title = {Nanostructural Effects on Thermoelectric Power of Graphene Nanoribbons},
      journal = {Japanese Journal of Applied Physics},
      publisher = {The Japan Society of Applied Physics},
      year = {2013},
      volume = {52},
      pages = {06GD05},
      doi = {http://dx.doi.org/10.1143/JJAP.52.06GD05}
    }
    
    Aleksandar Staykov & Petar Tzenov Current Rectification in Mono- and Bilayer Nanographenes with Different Edges 2013 J. Phys. Chem. C
    Vol. 117(26)The Journal of Physical Chemistry C, 13644-13653 
    DOI  
    Abstract: Graphene nanomaterials are actively used in electronics and materials science as elements of electric circuits and both structural and storage components. Their unique structure and electronic properties allow for a wide variety of applications (i.e., electron and thermal conductivity, ion transport, ion storage, and electric-current rectification). In this work, we investigate the electric-current-rectifying properties of mono- and bilayer two-terminal nanographene devices with the nonequilibrium Green's function method combined with density functional theory. The diode-like properties are achieved by control of the nanoribbons' edges. The sequential combination of armchair and zigzag domains leads to nanographene junctions with asymmetric current-voltage characteristics. The rectifying properties of the asymmetric armchair-zigzag carbon materials are derived from the nonequilibrium Green's function theory. The electric-current rectification is explained by the interaction of the external electric field induced between the electrodes with the localized electronic states within the junction. The model is applied on cyclophane molecules and bilayer nanographenes for which one of the layers consists of the armchair-edge nanoribbon, and the second layer consists of the zigzag?edge nanoribbon. Owing to the interlayer pi-pi stacking, the cyclophane and bilayer nanographene junctions show higher rectification ratios compared to the monolayer junctions. The proposed devices consist of nanographenes and polycyclic aromatic hydrocarbons, and the diode-like properties are obtained without heteroatom doping. The investigated carbon materials are promising candidates for current control elements in nanoelectronics.
    Keywords: ATK; Application; bilayer graphene; nanoribbon;
    Area: graphene
    BibTeX:
    @article{Staykov2013,
      author = {Staykov, Aleksandar and Tzenov, Petar},
      title = {Current Rectification in Mono- and Bilayer Nanographenes with Different Edges},
      booktitle = {The Journal of Physical Chemistry C},
      journal = {J. Phys. Chem. C},
      publisher = {American Chemical Society},
      year = {2013},
      volume = {117},
      number = {26},
      pages = {13644--13653},
      doi = {http://dx.doi.org/10.1021/jp402187a}
    }
    
    A. Sengupta, R.K. Ghosh & S. Mahapatra Performance Analysis of Strained Monolayer MoS2 MOSFET 2013 Electron Devices, IEEE Transactions on
    Vol. 60(9)Electron Devices, IEEE Transactions on, 2782-2787 
    DOI  
    Abstract: We present a computational study on the impact of tensile/compressive uniaxial e_xx and biaxial e_xx=e_yy strain on monolayer MoS2, n-, and p-MOSFETs. The material properties like band structure, carrier effective mass, and the multiband Hamiltonian of the channel are evaluated using the density functional theory. Using these parameters, self-consistent Poisson/Schrödinger solution under the nonequilibrium Green's function formalism is carried out to simulate the MOS device characteristics. 1.75% uniaxial tensile strain is found to provide a minor (6%) ON current improvement for the n-MOSFET, whereas same amount of biaxial tensile strain is found to considerably improve the p-MOSFET ON currents by 2-3 times. Compressive strain, however, degrades both n-MOS and p-MOS devices performance. It is also observed that the improvement in p-MOSFET can be attained only when the channel material becomes indirect gap in nature. We further study the performance degradation in the quasi-ballistic long-channel regime using a projected current method.
    Keywords: ATK; Application; effective mass; MOSFET circuits; materials; tensile strain; uniaxial strain, MoS2; density functional theory (DFT); nonequilibrium Green's function (NEGF); strain
    Area: 2dmat, tmd
    BibTeX:
    @article{Sengupta2013a,
      author = {Sengupta, A. and Ghosh, R.K. and Mahapatra, S.},
      title = {Performance Analysis of Strained Monolayer MoS2 MOSFET},
      booktitle = {Electron Devices, IEEE Transactions on},
      journal = {Electron Devices, IEEE Transactions on},
      year = {2013},
      volume = {60},
      number = {9},
      pages = {2782--2787},
      doi = {http://dx.doi.org/10.1109/TED.2013.2273456}
    }
    
    Serkan Caliskan Tuning the spin dependent behavior of monatomic carbon wires between nickel electrodes 2013 Physics Letters A
    Vol. 377(28-30), 1766-1773 
    DOI  
    Abstract: Abstract Spin polarized Density Functional Theory combined with Non-Equilibrium Green's Function Formalism is applied to investigate the spin dependent transport in carbon based monatomic systems. Both one-dimensional linear and ring structures sandwiched between spin polarized nickel electrodes are examined. Incorporating of nickel electrodes and rings leads to interesting spin dependent properties. The influence of electrode structure is also addressed, using the Ni(100) pyramidal and plane electrodes. It is revealed that spin dependent behavior is largely determined by the atomic arrangement of the monatomic system, and that both the transport and magnetic properties can be tuned by odd/even disparity and/or appropriate ring(s). The mechanisms governing the spin dependent properties in these structures are discussed.
    Keywords: ATK; Application; spin dependent transport; monatomic wires; nickel lead
    Area: molecular electronics; spin
    BibTeX:
    @article{Caliskan2013,
      author = {Caliskan, Serkan},
      title = {Tuning the spin dependent behavior of monatomic carbon wires between nickel electrodes},
      journal = {Physics Letters A},
      year = {2013},
      volume = {377},
      number = {28-30},
      pages = {1766--1773},
      doi = {http://dx.doi.org/10.1016/j.physleta.2013.05.007ggallium}
    }
    
    Can Cao, Ling-Na Chen, Meng-Qiu Long & Hui Xu Rectifying performance in zigzag graphene nanoribbon heterojunctions with different edge hydrogenations 2013 Physics Letters A
    Vol. 377(31-33), 1905-1910 
    DOI  
    Abstract: Using nonequilibrium Green's functions in combination with the density functional theory, we investigated the electronic transport behaviors of zigzag graphene nanoribbon (ZGNR) heterojunctions with different edge hydrogenations. The results show that electronic transport properties of ZGNR heterojunctions can be modulated by hydrogenations, and prominent rectification effects can be observed. We propose that the edge dihydrogenation leads to a blocking of electronic transfer, as well as the changes of the distribution of the frontier orbital at negative/positive bias might be responsible for the rectification effects. These results may be helpful for designing practical devices based on graphene nanoribbons.
    Keywords: ATK; Application; electronic transport property; zigzag graphene nanoribbon heterojunction; edge hydrogenation; rectifying effect
    Area: graphene
    BibTeX:
    @article{Cao2013,
      author = {Cao, Can and Chen, Ling-Na and Long, Meng-Qiu and Xu, Hui},
      title = {Rectifying performance in zigzag graphene nanoribbon heterojunctions with different edge hydrogenations},
      journal = {Physics Letters A},
      year = {2013},
      volume = {377},
      number = {31-33},
      pages = {1905--1910},
      doi = {http://dx.doi.org/10.1016/j.physleta.2013.05.004}
    }
    
    Satyendra Singh Chauhan, Pankaj Srivastava & Ashwani Kumar Shrivastava Electronic and transport properties of boron and nitrogen doped graphene nanoribbons: an ab initio approach 2013 Applied Nanoscience
    Vol. 4Applied Nanoscience, 1-7 
    DOI  
    Abstract: Graphene nanoribbons (GNRs) are expected to display extraordinary properties in the form of nanostructures. The effect of boron and nitrogen substitutional doping at four successive positions on electronic and transport properties of zigzag graphene nanoribbons (ZGNRs) is studied using spin-unpolarized density functional theory. It has been observed that the electronic structures of the doped ZGNRs are different from those of pristine ZGNRs. We have also calculated the transformation energy in the form of total energy. The substitutional boron atom at the nanoribbons edges suppresses the energy band near Fermi level by changing properties of material from metallic to semi-metallic in ZGNRs which can be explained as a consequence of the edge polarization effects. At all doping positions, N-doped ZGNRs are n-type while B-doped ZGNRs are p-type semiconductors. These substitutionally B- and N-doped impurities act as scattering centers for transport in GNRs. Due to unusual properties of these nanomaterials, they can be used in carbon-based nanoelectronics devices.
    Keywords: ATK; Application; graphene nanoribbons; density functional theory; boron; nitrogen; doping
    Area: graphene
    BibTeX:
    @article{Chauhan2013a,
      author = {Chauhan, Satyendra Singh and Srivastava, Pankaj and Shrivastava, Ashwani Kumar},
      title = {Electronic and transport properties of boron and nitrogen doped graphene nanoribbons: an ab initio approach},
      booktitle = {Applied Nanoscience},
      journal = {Applied Nanoscience},
      publisher = {Springer-Verlag},
      year = {2013},
      volume = {4},
      pages = {1-7},
      doi = {http://dx.doi.org/10.1007/s13204-013-0220-2}
    }
    
    R.M. Hariharan & D. John Thiruvadigal Effect of anchoring atoms on transport properties of a carbon-dimer based molecular junctions: a first principles study 2013 Nanosystems: Physics, Chemistry, Mathematics
    Vol. 4(2), 294-298 
    URL 
    Abstract: The conductance of a molecular device is sensitive to the contact geometry between the molecules and the probing electrodes. Combining the density functional theory calculations (DFT) for molecular electronic structure with a non-equilibrium Green's function (NEGF) method for electron transport, we calculate the molecular conductance of carbon dimer connected between Au leads through two different anchoring atoms Se and Te. The current-voltage characteristics and transmission spectra of two systems are studied. The results exhibit that, depending on the anchoring groups and the subsequent different metal-molecule chemical bonds, the current varies over more than four times of magnitude under the same bias. Furthermore, the system exhibits negative differential resistance (NDR) effect, when anchored with Te atom. This emphasizes the great importance of the anchoring groups in molecular devices.
    Keywords: ATK; Application; molecular electronics; anchoring group effects; electronic transport; first-principle; I-V characteristics
    Area: molecular electronics
    BibTeX:
    @article{Hariharan2013,
      author = {R. M. Hariharan and D. John Thiruvadigal},
      title = {Effect of anchoring atoms on transport properties of a carbon-dimer based molecular junctions: a first principles study},
      journal = {Nanosystems: Physics, Chemistry, Mathematics},
      year = {2013},
      volume = {4},
      number = {2},
      pages = {294-298},
      url = {http://nanojournal.ifmo.ru/articles/volume4/4-2/mam-12/paper17/}
    }
    
    C. Preferencial Kala, P. Aruna Priya & D. John Thiruvadigal Investigation of Terminal Group Effect on Electron Transport Through Open Molecular Structures 2013 Communications in Theoretical Physics
    Vol. 59(5), 649-654 
    DOI  
    Abstract: The effect of terminal groups on the electron transport through metal-molecule-metal system has been investigated using nonequilibrium Green's function (NEGF) formalism combined with extended Huckel theory (EHT). Au-molecule-Au junctions are constructed with borazine and BCN unit structure as core molecule and sulphur (S), oxygen (O), selenium (Se) and cyano-group (CN) as terminal groups. The electron transport characteristics of the borazine and BCN molecular systems are analyzed through the transmission spectra and the current-voltage curve. The results demonstrate that the terminal groups modifying the transport behaviors of these systems in a controlled way. Our result shows that, selenium is the best linker to couple borazine to Au electrode and oxygen is the best one to couple BCN to Au electrode. Furthermore, the results of borazine systems are compared with that of BCN molecular systems and are discussed. Simulation results show that the conductance through BCN molecular systems is four times larger than the borazine molecular systems. Negative differential resistance behavior is observed with borazine-CN system and the saturation feature appears in BCN systems.
    Keywords: ATK-SE; Application; molecular electronics; extended Huckel theory (EHT); nonequilibrium Green's function (NEGF); quantum transport
    Area: molecular electronics
    BibTeX:
    @article{Kala2013,
      author = {C. Preferencial Kala and P. Aruna Priya and D. John Thiruvadigal},
      title = {Investigation of Terminal Group Effect on Electron Transport Through Open Molecular Structures},
      journal = {Communications in Theoretical Physics},
      year = {2013},
      volume = {59},
      number = {5},
      pages = {649-654},
      doi = {http://dx.doi.org/10.1088/0253-6102/59/5/21}
    }
    
    Manabu Kiguchi, Junichi Inatomi, Yuuta Takahashi, Ryota Tanaka, Takafumi Osuga, Takashi Murase, Makoto Fujita, Tomofumi Tada & Satoshi Watanabe Highly Conductive [3 x n] Gold-Ion Clusters Enclosed within Self-Assembled Cages 2013 Angew. Chem. Int. Ed.
    Vol. 52(24), 6202-6205 
    DOI  
    Keywords: ATK; Application; cluster compounds; electron transfer; gold; molecular electronics; single-molecule studies
    Area: molecular electronics
    BibTeX:
    @article{Kiguchi2013,
      author = {Kiguchi, Manabu and Inatomi, Junichi and Takahashi, Yuuta and Tanaka, Ryota and Osuga, Takafumi and Murase, Takashi and Fujita, Makoto and Tada, Tomofumi and Watanabe, Satoshi},
      title = {Highly Conductive [3 x n] Gold-Ion Clusters Enclosed within Self-Assembled Cages},
      journal = {Angew. Chem. Int. Ed.},
      publisher = {WILEY-VCH Verlag},
      year = {2013},
      volume = {52},
      number = {24},
      pages = {6202--6205},
      doi = {http://dx.doi.org/10.1002/anie.201301665}
    }
    
    Vijay K. Lamba & O.P. Garg Modelling of Junctions between ZnO Rods/Nano Ribbons and Gold Electrodes 2012 Journal of Environmental Science, Computer Science and Engineering and Technology
    Vol. 1(3), 499 
    URL 
    Abstract: Using first-principles density functional theory calculations, various junction smodels constructed from different ZnO structures (i.e. rods & nano ribbons) and Gold electrodes/films units via covalent linkage have been envisioned. These models consist of linear, T, H, and L-shaped junctions within the connection modes between ZnO structures (i.e. rods & nano ribbons) and Gold electrodes/films units. The transport properties of the designed junctions were calculated with Atomistix Toolkit which is based on the combination of DFT with the non-equilibrium Green's function (NEGF) formalism. The NEGF-DFT approach has now become standard and is utilized extensively to describe and predict the behavior of different molecular junctions. The NEGF formulation has an inherent elegance and generality, which makes it an attractive way to approach these issues. The simulation procedure is as follows: the self-consistent potential of two electrodes is calculated first, which will be shifted strictly with each other by external bias. Then, the electron density of the central scattering region is obtained from the Green's function. When the electron density is known, the DFT Hamiltonian matrix can be computed using boundary conditions. This procedure is iterated until self-consistency is achieved. The simulation results obtained for geometrical properties, binding effects, Linear, T, H, and L shaped metal-metal junctions, and Linear, T, H, and L shaped metalsemiconductor junctions suggested that the proposed models are promising for future applications in designing and fabrication of nano generator using ZnO rods.
    Keywords: ATK; Application; nanowire; junctions; NEGF; DFT; Two Probe Systems
    Area: nanowires
    BibTeX:
    @article{Lamba2012a,
      author = {Vijay K. Lamba and O. P. Garg},
      title = {Modelling of Junctions between ZnO Rods/Nano Ribbons and Gold Electrodes},
      journal = {Journal of Environmental Science, Computer Science and Engineering and Technology},
      year = {2012},
      volume = {1},
      number = {3},
      pages = {499},
      url = {http://www.jecet.org/}
    }
    
    Zheng Li, Jiaxin Zheng, Zeyuan Ni, Ruge Quhe, Yangyang Wang, Zhengxiang Gao & Jing Lu Intrinsic region length scaling of heavily doped carbon nanotube p-i-n junctions 2013 Nanoscale
    Vol. 5(15), 6999-7004 
    DOI  
    Abstract: We investigated the dependence of the transport properties of heavily doped intratube single-walled carbon nanotube (SWCNT) p-i-n junctions on the length of the intrinsic region by using empirical self-consistent quantum transport simulations. When the length of the intrinsic region is scaled from a few angstroms to over 10 nanometers, the SWCNT p-i-n junction evolves from a tunneling diode with a large negative rectification and large negative differential resistance to one with a large positive rectification (like a conventional positive rectifying diode). The critical length of the intrinsic length is about 8.0 nm. Therefore, one can obtain nanoscale diodes of different performance types by changing the intrinsic region length.
    Keywords: ATK; Application; nanotube; doping; rectification; field-effect transistors; thin insulating film; rectification; formula; diodes
    Area: nanotubes
    BibTeX:
    @article{Li2013b,
      author = {Li, Zheng and Zheng, Jiaxin and Ni, Zeyuan and Quhe, Ruge and Wang, Yangyang and Gao, Zhengxiang and Lu, Jing},
      title = {Intrinsic region length scaling of heavily doped carbon nanotube p-i-n junctions},
      journal = {Nanoscale},
      publisher = {The Royal Society of Chemistry},
      year = {2013},
      volume = {5},
      number = {15},
      pages = {6999--7004},
      doi = {http://dx.doi.org/10.1039/C3NR01462B}
    }
    
    J. Li, Z.H. Zhang, G. Kwong, W. Tian, Z.Q. Fan & X.Q. Deng A new exploration on the substantial improvement of rectifying behaviors for a donor-acceptor molecular diode by graphene electrodes 2013 Carbon
    Vol. 61(0), 284-293 
    DOI  
    Abstract: Sandwiching a donor-acceptor molecule between two graphene nanoribbon (GNR) electrodes to construct a particular molecular diode, our calculations from the first-principles method predict that such a configuration can lead to dramatically different and unexpected effects. When the GNR electrodes are semiconducting, the rectifying behaviors for this molecule can be enhanced greatly. The maximum rectification ratio rises sharply with an increase of the bandgap size of GNR electrodes and can reach a value more than 4000 as the bandgap is about 0.8 eV, which is of a very significant improvement as compared with previously investigated results for such a molecule coupled to bulk metal electrodes. Therefore, our studies imply that using graphene with a large bandgap as electrodes might be a novel effective pathway to greatly raise rectifying behaviors of a donor-acceptor molecule.
    Keywords: ATK; Application; graphene nanoribbon; doping; rectification; diode; transport properties; room-temperature
    Area: graphene
    BibTeX:
    @article{Li2013c,
      author = {Li, J. and Zhang, Z.H. and Kwong, G. and Tian, W. and Fan, Z.Q. and Deng, X.Q.},
      title = {A new exploration on the substantial improvement of rectifying behaviors for a donor-acceptor molecular diode by graphene electrodes},
      journal = {Carbon},
      year = {2013},
      volume = {61},
      number = {0},
      pages = {284--293},
      doi = {http://dx.doi.org/10.1016/j.carbon.2013.05.006}
    }
    
    Amretashis Sengupta & Santanu Mahapatra Performance limits of transition metal dichalcogenide (MX[sub 2]) nanotube surround gate ballistic field effect transistors 2013 Journal of Applied Physics
    Vol. 113(19), 194502 
    DOI  
    Abstract: We theoretically analyze the performance of transition metal dichalcogenide (MX2) single wall nanotube (SWNT) surround gate MOSFET, in the 10 nm technology node. We consider semiconducting armchair (n, n) SWNT of MoS2, MoSe2, WS2, and WSe2 for our study. The material properties of the nanotubes are evaluated from the density functional theory, and the ballistic device characteristics are obtained by self-consistently solving the Poisson-Schrödinger equation under the non-equilibrium Green's function formalism. Simulated ON currents are in the range of 61-76 muA for 4.5 nm diameter MX2 tubes, with peak transconductance 175-218 muS and ON/OFF ratio 0.6e-5 to 0.8e-5. The subthreshold slope is 62.22 mV/decade and a nominal drain induced barrier lowering of 12-15 mV/V is observed for the devices. The tungsten dichalcogenide nanotubes offer superior device output characteristics compared to the molybdenum dichalcogenide nanotubes, with WSe2 showing the best performance. Studying SWNT diameters of 2.5-5 nm, it is found that increase in diameter provides smaller carrier effective mass and 4%-6% higher ON currents. Using mean free path calculation to project the quasi-ballistic currents, 62%-75% reduction from ballistic values in drain current in long channel lengths of 100, 200 nm is observed.
    Keywords: ATK; Application; dichalcogenides; nanotube; field effect transistor; gate all around;s
    Area: nanotubes; dichalcogenides
    BibTeX:
    @article{Sengupta2013,
      author = {Sengupta, Amretashis and Mahapatra, Santanu},
      title = {Performance limits of transition metal dichalcogenide (MX[sub 2]) nanotube surround gate ballistic field effect transistors},
      journal = {Journal of Applied Physics},
      publisher = {AIP},
      year = {2013},
      volume = {113},
      number = {19},
      pages = {194502},
      doi = {http://dx.doi.org/10.1063/1.4805059}
    }
    
    Anurag Srivastava, Noopur Jain & A.K. Nagawat Effect of Stone-Wales Defects on Electronic Properties of CNTs: Ab-Initio Study 2013 Quantum Matter
    Vol. 2(4), 307-313 
    DOI  
    Abstract: Present paper discusses the ab-initio > analysis of electronic properties of zigzag carbon nanotubes (CNTs) on increasing the number of Stone-Wales (SW) defects. Computation has been performed by using local density approximation (LDA) under Perdew-Zunger (PZ) parameterization as exchange correlation functional. Analysis depicts an interesting variation in band gap with increase in number of SW defects introduced in zigzag CNTs with n = 7, 8, and 9. The comparative band gap progression with number of SW defects in the three nanotubes have also been analyzed and discussed in detail.
    Keywords: ATK; Application; electronic properties; ab-initio; carbon nanotube; CNT; Stone-Wales defects
    Area: nanotubes
    BibTeX:
    @article{Srivastava2013a,
      author = {Srivastava, Anurag and Jain, Noopur and Nagawat, A.K.},
      title = {Effect of Stone-Wales Defects on Electronic Properties of CNTs: Ab-Initio Study},
      journal = {Quantum Matter},
      year = {2013},
      volume = {2},
      number = {4},
      pages = {307--313},
      doi = {http://dx.doi.org/10.1166/qm.2013.1061}
    }
    
    G.P. Tang, J.C. Zhou, Z.H. Zhang, X.Q. Deng & Z.Q. Fan A theoretical investigation on the possible improvement of spin-filter effects by an electric field for a zigzag graphene nanoribbon with a line defect 2013 Carbon
    Vol. 60(0), 94-101 
    DOI  
    Abstract: The spin-polarized electronic properties for a zigzag-edge graphene nanoribbon (ZGNR) with an extended line defect are investigated, particularly focusing on controlling the effects of an external transverse electric field (Eext). An ab initio scanning tunneling microscope image for the defective ZGNR is also predicted. Results show that such a ZGNR can exhibit a strong spin polarization and ferromagnetic state, and the spin-filter effect can be significantly tuned and improved by the Eext. The spin-filter efficiency for our proposed device is predicted to be able to reach up to 60-81% in a large bias range of 0-0.6 V at Eext = 3.0 V/nm. Mechanisms for such results and the experimental feasibility for the device are suggested. These findings suggest a new possibility for developing nanometer-scale all-carbon spintronic devices.
    Keywords: ATK; Application; graphene; defect; spin filter; spintronics
    Area: graphene; spin
    BibTeX:
    @article{Tang2013,
      author = {Tang, G.P. and Zhou, J.C. and Zhang, Z.H. and Deng, X.Q. and Fan, Z.Q.},
      title = {A theoretical investigation on the possible improvement of spin-filter effects by an electric field for a zigzag graphene nanoribbon with a line defect},
      journal = {Carbon},
      year = {2013},
      volume = {60},
      number = {0},
      pages = {94--101},
      doi = {http://dx.doi.org/10.1016/j.carbon.2013.04.002}
    }
    
    Mayank Chakraverty & Harish M. Kittur First Principle Simulations of Fe/MgO/Fe Magnetic Tunnel Junctions for Applications in Magnetoresistive Random Access Memory Based Cell Phone Architectures 2011 International Journal of Micro and Nano Systems
    Vol. 2(1), 1-6 
    URL 
    Abstract: Fe/MgO/Fe magnetic tunnel junctions (MTJs) have been reported to have very high tunnel magnetoresistance (TMR) ratios. In this work, we present the results of First Principle simulations of Fe/MgO/Fe MTJs with LSDA as the exchange correlation. The I-V characteristics in the antiparallel magnetization state exhibit strong features. The bias dependence of the TMR ratio shows nearly 100% TMR ratios for bias voltages up to 1.5 Volts. The MgO thickness dependence of the tunnel resistance shows the expected exponential increase in the tunnel resistance. The write energy per bit and power consumption have been computed for a bias voltage of 0.5 Volts. The Fe/MgO/Fe MTJs are the most widely used MTJs, integrated with NMOS transistors, in the form of MTJ based Magnetoresistive Random Access Memory (MRAM) which is an advanced memory technology operating at the nano scale. MRAMs are spintronic devices.
    Keywords: ATK; Application; spin; first Principle; LSDA; MTJ; TMR
    Area: interfaces; nvm; spin
    BibTeX:
    @article{Chakraverty2011,
      author = {Mayank Chakraverty and Harish M. Kittur},
      title = {First Principle Simulations of Fe/MgO/Fe Magnetic Tunnel Junctions for Applications in Magnetoresistive Random Access Memory Based Cell Phone Architectures},
      journal = {International Journal of Micro and Nano Systems},
      year = {2011},
      volume = {2},
      number = {1},
      pages = {1-6},
      url = {http://www.serialsjournals.com/articles.php?volumesno_id=276&journals_id=148&volumes_id=461}
    }
    
    Mayank Chakraverty & Harish M. Kittur First Principle Study of Tunnel Currents through CeO2, Y2O3, TiO2 and Al2O3 Dielectrics in MOSFETs for Ultra Large Scale Integration 2012 Advanced Materials Research
    Vol. 584, 428-432 
    DOI  
    Abstract: High gate leakage current, as a central problem, has decelerated the downscaling of minimum feature size of the field effect transistors In this paper, a combination of density functional theory and non equilibrium Green's function formalism has been applied to the atomic scale calculation of the tunnel currents through CeO2, Y2O3, TiO2 and Al2O3 dielectrics in MOSFETs. The tunnel currents for different bias voltages applied to Si/Insulator/Si systems have been obtained along with tunnel conductance v/s bias voltage plots for each system. The results are in agreement to the use of high dielectric constant materials as gate dielectric so as to enable further downscaling of MOSFETs with reduced gate leakage currents thereby enabling ultra large scale integration. When used as dielectric, TiO2 exhibits extremely low tunnel currents followed by Y2O3 while CeO2 and Al2O3 exhibit high tunnel currents through them at certain bias voltages.
    Keywords: ATK; Application; CMOS; FIBL; leakage current; MOSFET; threshold voltage; ULSI
    Area: interfaces; semi
    BibTeX:
    @article{Chakraverty2012a,
      author = {Mayank Chakraverty and Harish M. Kittur},
      title = {First Principle Study of Tunnel Currents through CeO2, Y2O3, TiO2 and Al2O3 Dielectrics in MOSFETs for Ultra Large Scale Integration},
      journal = {Advanced Materials Research},
      year = {2012},
      volume = {584},
      pages = {428-432},
      doi = {http://dx.doi.org/10.4028/www.scientific.net/AMR.584.428}
    }
    
    Mayank Chakraverty, P. Arun Kumar & Harish M Kittur Performance Analysis of Fe/SiO2/Fe MTJ and Ni/Al2O3/Ni MTJ based Magnetoresistive Random Access Memories 2012 Journal of VLSI Design Tools & Technology
    Vol. 2(2), 1 
    URL 
    Abstract: This paper reports the first principle simulations of Fe/SiO2/Fe and Ni/Al2O3/Ni magnetic tunnel junctions (MTJs). A performance analysis has been done based upon the device-level simulations of the two magnetic tunnel junctions followed by the circuit level simulations of magnetoresistive random access memory (MRAM) cell operating with the two MTJs respectively. From the device-level simulations, the two MTJs have been compared with regard to the bias dependence of TMR ratios, insulator thickness dependence of TMR ratios and insulator thickness dependence of parallel and anti-parallel state resistances taking the relative magnetizations of the two ferromagnetic films of the MTJs into consideration. From the circuit-level simulations, the static and switching power dissipations have been computed along with the delay time estimation.
    Keywords: ATK; Application; MTJ; spin;
    Area: interfaces; nvm; spin
    BibTeX:
    @article{Chakraverty2012b,
      author = {Mayank Chakraverty and P. Arun Kumar and Harish M Kittur},
      title = {Performance Analysis of Fe/SiO2/Fe MTJ and Ni/Al2O3/Ni MTJ based Magnetoresistive Random Access Memories},
      journal = {Journal of VLSI Design Tools & Technology},
      year = {2012},
      volume = {2},
      number = {2},
      pages = {1},
      url = {http://www.stmjournals.com/index.php?journal=JoVDTT&page=article&op=view&path[]=2244}
    }
    
    Mayank Chakraverty & Harish M Kittur Comparison of tunnel currents through SiO2, HfO2, Ta2O5, ZrO2 and Dy2O3 dielectrics in MOS devices for ultra large scale integration using first principle calculations 2013 Emerging Research Areas and 2013 International Conference on Microelectronics, Communications and Renewable Energy (AICERA/ICMiCR), 2013 Annual International Conference on, 1-6  DOI  
    Abstract: The work presented in this paper focuses on the effects of high leakage current in field effect transistors and the possible ways to play down with the leakage currents. This paper combines density functional theory and non equilibrium Green's function formalism to perform atomic scale calculation of tunnel currents through SiO2, HfO2, Ta2O5ZrO2 and DY2O3 dielectrics in MOSFETs. The tunnel currents for different bias voltages applied to Si/Insulator/Si systems have been obtained along with tunnel conductance v/s bias voltage plots for each system and the plots have been analyzed with reference to the presently used bulk Si/SiO2/Si systems that have SiO2 as the gate dielectric material. The results justify the use of high dielectric constant materials as gate dielectric in FET devices so as to enable further downscaling of MOSFETs with reduced gate leakage currents thereby enabling ultra large scale integration.
    Keywords: ATK; Application; dielectrics; insulators; leakage currents; logic gates;MOSFET;Silicon;CMOS;Gate Leakage current;MOSFETS;drive current;threshold voltage;transconductance;tunnel current
    Area: interfaces; semi
    BibTeX:
    @inproceedings{Chakraverty2013,
      author = {Chakraverty, Mayank and Kittur, Harish M},
      title = {Comparison of tunnel currents through SiO2, HfO2, Ta2O5, ZrO2 and Dy2O3 dielectrics in MOS devices for ultra large scale integration using first principle calculations},
      booktitle = {Emerging Research Areas and 2013 International Conference on Microelectronics, Communications and Renewable Energy (AICERA/ICMiCR), 2013 Annual International Conference on},
      year = {2013},
      pages = {1-6},
      doi = {http://dx.doi.org/10.1109/AICERA-ICMiCR.2013.6575936}
    }
    
    Wei Liu, Jiahao Kang, Deblina Sarkar, Yasin Khatami, Debdeep Jena & Kaustav Banerjee Role of Metal Contacts in Designing High-Performance Monolayer n-Type WSe2 Field Effect Transistors 2013 Nano Lett.
    Vol. 13(5)Nano Letters, 1983-1990 
    DOI  
    Abstract: This work presents a systematic study toward the design and first demonstration of high-performance n-type monolayer tungsten diselenide (WSe2) field effect transistors (FET) by selecting the contact metal based on understanding the physics of contact between metal and monolayer WSe2. Device measurements supported by ab initio density functional theory (DFT) calculations indicate that the d-orbitals of the contact metal play a key role in forming low resistance ohmic contacts with monolayer WSe2. On the basis of this understanding, indium (In) leads to small ohmic contact resistance with WSe2 and consequently, back-gated In-WSe2 FETs attained a record ON-current of 210 microA/micrometer, which is the highest value achieved in any monolayer transition-metal dichalcogenide- (TMD) based FET to date. An electron mobility of 142 cm2/Vs (with an ON/OFF current ratio exceeding 10^6) is also achieved with In-WSe2 FETs at room temperature. This is the highest electron mobility reported for any back gated monolayer TMD material till date. The performance of n-type monolayer WSe2 FET was further improved by Al2O3 deposition on top of WSe2 to suppress the Coulomb scattering. Under the high-k dielectric environment, electron mobility of Ag-WSe2 FET reached ~202 cm2/Vs with an ON/OFF ratio of over 10^6 and a high ON-current of 205 microA/micrometer. In tandem with a recent report of p-type monolayer WSe2 FET (Fang, H. et al. Nano Lett. 2012, 12, (7), 3788-3792), this demonstration of a high-performance n-type monolayer WSe2 FET corroborates the superb potential of WSe2 for complementary digital logic applications.
    Keywords: ATK; Application; 2D semiconductors; contact resistance; field-effect-transistor; monolayer; transition-metal dichalcogenides; tungsten diselenide; WSe2
    Area: 2dmat, tmd
    BibTeX:
    @article{Liu2013b,
      author = {Liu, Wei and Kang, Jiahao and Sarkar, Deblina and Khatami, Yasin and Jena, Debdeep and Banerjee, Kaustav},
      title = {Role of Metal Contacts in Designing High-Performance Monolayer n-Type WSe2 Field Effect Transistors},
      booktitle = {Nano Letters},
      journal = {Nano Lett.},
      publisher = {American Chemical Society},
      year = {2013},
      volume = {13},
      number = {5},
      pages = {1983--1990},
      doi = {http://dx.doi.org/10.1021/nl304777e}
    }
    
    Yun Ni, Kai-Lun Yao, Hua-Hua Fu, Guo-Ying Gao, Si-Cong Zhu, Bo Luo, Shu-Ling Wang & Rui-Xue Li The transport properties and new device design: the case of 6,6,12-graphyne nanoribbons 2013 Nanoscale
    Vol. 5(10), 4468-4475 
    DOI  
    Abstract: By performing first-principle quantum transport calculations, we studied the transport properties of three kinds of 6,6,12-graphyne nanoribbons with different edges and different cutting directions. The nanoribbon with zigzag edges shows metallic properties and the spin-polarized currents show an obvious negative differential resistance effect, the other two nanoribbons terminated by a phenyl ring are semiconductors and spin-unpolarized. We also designed several nanowire devices based on these 6,6,12-graphyne nanoribbons, such as rectifier, spin filter diode, spin FET and spin caloritronics devices. These results indicate that 6,6,12-graphyne is a potential candidate for spintronics and spin caloritronics.
    Keywords: ATK; Application; spin; graphene; graphyne nanoribbon; spintronics; caloritronics; negative differential resistance; NDR;
    Area: graphene; spin; thermo
    BibTeX:
    @article{Ni2013a,
      author = {Ni, Yun and Yao, Kai-Lun and Fu, Hua-Hua and Gao, Guo-Ying and Zhu, Si-Cong and Luo, Bo and Wang, Shu-Ling and Li, Rui-Xue},
      title = {The transport properties and new device design: the case of 6,6,12-graphyne nanoribbons},
      journal = {Nanoscale},
      publisher = {The Royal Society of Chemistry},
      year = {2013},
      volume = {5},
      number = {10},
      pages = {4468--4475},
      doi = {http://dx.doi.org/10.1039/C3NR00731F}
    }
    
    Zhenhua Zhang, Chao Guo, Denise Jeng Kwong, Jie Li, Xiaoqing Deng & Zhiqiang Fan A Dramatic Odd-Even Oscillating Behavior for the Current Rectification and Negative Differential Resistance in Carbon-Chain-Modified Donor-Acceptor Molecular Devices 2013 Advanced Functional Materials
    Vol. 23(21), 2765-2774 
    DOI  
    Abstract: The donor-acceptor molecule is the only molecule that features a real intrinsic rectification. However, all investigations in the last decades showed that rectification behaviors of such molecules are not promising since their rectification ratio is only on the order of 10. Use of carbon chains C_n to serve as spacers is reported, along with attempts to modulate electrical behavior of the donor-acceptor molecule. Calculations using the first-principles method show that electrical behavior is indeed altered substantively, and a particular regularity can be clearly observed, i.e., a dramatic odd-even oscillation for electronic behavior with increasing carbon-chain length n. For models with even-n carbon chains, the rectification ratio is small (30), and no negative differential resistance (NDR) behavior is detected, but the rectifying performance of models with odd-n carbon chains is tremendously improved and rectification ratios on the order of 50 to 400 can be achieved, alongside a large NDR. This study thus suggests that using a suitable spacer might be an effective way to significantly boost electrical characteristics, including rectifying performance, of the donor-acceptor molecule.
    Keywords: ATK; Application; molecular electronics; donor-acceptor molecule: negative differential resistance; NDR; molecular devices; carbon chains; rectification behavior;
    Area: molecular electronics
    BibTeX:
    @article{Zhang2013a,
      author = {Zhang, Zhenhua and Guo, Chao and Kwong, Denise Jeng and Li, Jie and Deng, Xiaoqing and Fan, Zhiqiang},
      title = {A Dramatic Odd-Even Oscillating Behavior for the Current Rectification and Negative Differential Resistance in Carbon-Chain-Modified Donor-Acceptor Molecular Devices},
      journal = {Advanced Functional Materials},
      year = {2013},
      volume = {23},
      number = {21},
      pages = {2765--2774},
      doi = {http://dx.doi.org/10.1002/adfm.201201790}
    }
    
    Andreas Zienert, Jörg Schuster & Thomas Gessner Extended Hückel Theory for Carbon Nanotubes: Band Structure and Transport Properties 2013 J. Phys. Chem. A
    Vol. 117(17)The Journal of Physical Chemistry A, 3650-3654 
    DOI  
    Abstract: Extended Hückel theory (EHT) is a well established method for the description of the electronic structure of molecules and solids. In this article, we present a set of extended Hückel parameters for carbon nanotubes (CNTs), obtained by fitting the ab initio band structure of the (6,0) CNT. The new parameters are highly transferable to different types of CNTs. To demonstrate the versatility of the approach, we perform self-consistent EHT-based electron transport calculations for finite length CNTs with metal electrodes.
    Keywords: ATK-SE; Application; carbon nanotube; NEGF; pseudopotentials; interconnect; transistor; sensors; gaps
    Area: nanotubes
    BibTeX:
    @article{Zienert2013,
      author = {Zienert, Andreas and Schuster, Jörg and Gessner, Thomas},
      title = {Extended Hückel Theory for Carbon Nanotubes: Band Structure and Transport Properties},
      booktitle = {The Journal of Physical Chemistry A},
      journal = {J. Phys. Chem. A},
      publisher = {American Chemical Society},
      year = {2013},
      volume = {117},
      number = {17},
      pages = {3650--3654},
      doi = {http://dx.doi.org/10.1021/jp312586j}
    }
    
    Somobrata Acharya, Bidisa Das, Umamahesh Thupakula, Katsuhiko Ariga, D.D. Sarma, Jacob Israelachvili & Yuval Golan A Bottom-Up Approach toward Fabrication of Ultrathin PbS Sheets 2013 Nano Lett.
    Vol. 13(2)Nano Letters, 409-415 
    DOI  
    Abstract: Two-dimensional (2D) sheets are currently in the spotlight of nanotechnology owing to high-performance device fabrication possibilities. Building a free-standing quantum sheet with controlled morphology is challenging when large planar geometry and ultranarrow thickness are simultaneously concerned. Coalescence of nanowires into large single-crystalline sheet is a promising approach leading to large, molecularly thick 2D sheets with controlled planar morphology. Here we report on a bottom-up approach to fabricate high-quality ultrathin 2D single crystalline sheets with well-defined rectangular morphology via collective coalescence of PbS nanowires. The ultrathin sheets are strictly rectangular with 1.8 nm thickness, 200-250 nm width, and 3-20 micrometer length. The sheets show high electrical conductivity at room and cryogenic temperatures upon device fabrication. Density functional theory (DFT) calculations reveal that a single row of delocalized orbitals of a nanowire is gradually converted into several parallel conduction channels upon sheet formation, which enable superior in-plane carrier conduction.
    Keywords: ATK; Application; nanowires; ultrathin sheet; coalescence; activation energy; DFT calculations; transport; metal-insulator-transition; Langmuir monolayers; ballistic transport; oriented attachment; suspended graphene; room-temperature; nanowires; superlattices; nanocrystals
    Area: nanowires
    BibTeX:
    @article{Acharya2013,
      author = {Acharya, Somobrata and Das, Bidisa and Thupakula, Umamahesh and Ariga, Katsuhiko and Sarma, D. D. and Israelachvili, Jacob and Golan, Yuval},
      title = {A Bottom-Up Approach toward Fabrication of Ultrathin PbS Sheets},
      booktitle = {Nano Letters},
      journal = {Nano Lett.},
      publisher = {American Chemical Society},
      year = {2013},
      volume = {13},
      number = {2},
      pages = {409--415},
      doi = {http://dx.doi.org/10.1021/nl303568d}
    }
    
    Zhaoqiang Bai, Yongqing Cai, Lei Shen, Guchang Han & Yuanping Feng High-performance giant-magnetoresistance junctions based on the all-Heusler architecture with matched energy bands and Fermi surfaces 2013 Applied Physics Letters
    Vol. 102(15), 152403 
    DOI  
    Abstract: We present an all-Heusler architecture which could be used as a rational design scheme for achieving high spin-filter efficiency in the current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices. A Co2MnSi/Ni2NiSi/Co2MnSi trilayer stack is chosen as the prototype of such an architecture, of which the electronic structure and magnetotransport properties are systematically investigated by first principles approaches. Well matched energy bands and Fermi surfaces between the all-Heusler electrode-spacer pair are found, which, in combination with the electrode half-metallicity, indicate large bulk and interfacial spin-asymmetry, high spin-filter efficiency, and consequently good magnetoresistance performance. Transport calculations further confirm the superiority of the all-Heusler architecture over the conventional Heusler/transition-metal structure by comparing their transmission coefficients and interfacial resistances of parallel conduction electrons, as well as the macroscopic current-voltage characteristics. We suggest future theoretical and experimental efforts in developing high-performance all-Heusler CPP-GMR junctions for the read heads of the next generation high-density hard disk drives.
    Keywords: ATK; Application; interfaces; spin; semi; ab initio calculations, band structure, cobalt alloys, Fermi surface, giant magnetoresistance, manganese alloys, multilayers, nickel alloys, silicon alloys, spin systems
    Area: interfaces; spin; semi; nvm
    BibTeX:
    @article{Bai2013a,
      author = {Bai, Zhaoqiang and Cai, Yongqing and Shen, Lei and Han, Guchang and Feng, Yuanping},
      title = {High-performance giant-magnetoresistance junctions based on the all-Heusler architecture with matched energy bands and Fermi surfaces},
      journal = {Applied Physics Letters},
      publisher = {AIP},
      year = {2013},
      volume = {102},
      number = {15},
      pages = {152403},
      doi = {http://dx.doi.org/10.1063/1.4802581}
    }
    
    S. Barzilai, F. Tavazza & L.E. Levine First-principle modeling of gold adsorption on BeO (0001) 2013 Surface Science
    Vol. 609(0), 39-43 
    DOI  
    Abstract: Gold nanowire chains are considered a good candidate for nanoelectronic devices since they exhibit remarkable structural and electrical properties. For practical engineering devices, alpha-wurtzite BeO may be a useful platform for supporting these nanowires, since the atom separation of the BeO (0001) surface is compatible with the Au-Au atom spacing. However, its influence on the nanowire conductivity is unknown. Here, ab initio simulations of adsorption of one gold atom on cleaved BeO (0001) surfaces have been performed to find the most favorable adsorption site. An attractive adsorption was obtained for all the studied sites, but the most favorable site was above the oxygen for the O-terminated surface and above the Be-Be bridge for the Be-terminated surface. A relatively high electron density is observed in the AuO and AuBe bonds, and the local density of states exhibits high peaks in the vicinity of the Fermi energy.
    Keywords: ATK; Application; BeO; ab-initio calculations, adsorption, substrate; geometry optimization; band-structure; surfaces; conductance; molecules; chains; oxide
    Area: nanowires
    BibTeX:
    @article{Barzilai2013a,
      author = {Barzilai, S. and Tavazza, F. and Levine, L.E.},
      title = {First-principle modeling of gold adsorption on BeO (0001)},
      journal = {Surface Science},
      year = {2013},
      volume = {609},
      number = {0},
      pages = {39--43},
      doi = {http://dx.doi.org/10.1016/j.susc.2012.10.017}
    }
    
    Nikolai Lebedev, Igor Griva & Anders Blom Internal Control of Electron Transfer through a Single Iron Atom by Chelating Porphyrin 2013 J. Phys. Chem. C
    Vol. 117(14)The Journal of Physical Chemistry C, 6933-6939 
    DOI  
    Abstract: Construction of efficient and highly integrated electronic devices is the main challenge and goal of nanoelectronics. The main problem in the construction of such devices is the fusion between conducting and controlling parts of the device, substantially reducing the efficiency of regulation. To approach the problem we study the electron transfer through a carbon nanotube (CNT)-histidine-heme-histidine-CNT conjugate with an orthogonal porphyrin orientation relative to the CNT electrodes. Using density functional theory and nonequilibrium Green's function calculations we show that at low bias the CNT molecular orbitals are electronically coupled only to the Fe atom but uncoupled from the tetrapyrrole ring of the porphyrin. We found that at low bias the electrons pass exclusively through the central Fe atom of the porphyrin, but at higher bias they are partially scattered by the tetrapyrrole ring, leading to a reduction of the total current through the molecule (negative differential resistance). This allows for keeping the electron flow through the device at a specific level and for controlling the current through the device by the redox state of the tetrapyrrole ring. In the orthogonal orientation, neither of the porphyrin side groups directly participates in the electron transfer through the heme and can thus be used for porphyrin binding and orientation to proteins or electrodes. These results open the possibility for the construction of a highly integrated electronic field effect transistor in a single molecule with controllable electron transfer through individual iron atoms.
    Keywords: ATK; Application; molecular electronics; nanotube; negative differential resistance; histidine; heme; porphyrin;
    Area: molecular electronics
    BibTeX:
    @article{Lebedev2013,
      author = {Lebedev, Nikolai and Griva, Igor and Blom, Anders},
      title = {Internal Control of Electron Transfer through a Single Iron Atom by Chelating Porphyrin},
      booktitle = {The Journal of Physical Chemistry C},
      journal = {J. Phys. Chem. C},
      publisher = {American Chemical Society},
      year = {2013},
      volume = {117},
      number = {14},
      pages = {6933--6939},
      doi = {http://dx.doi.org/10.1021/jp311686c}
    }
    
    Lili Lin, Jun Jiang & Yi Luo Elastic and inelastic electron transport in metal-molecule(s)-metal junctions 2013 Physica E: Low-dimensional Systems and Nanostructures
    Vol. 47(0), 167-187 
    DOI URL 
    Abstract: An overview of studies on elastic and inelastic electron transport properties of molecular junction devices is presented. The development of the experimental fabrication and characterization of molecular junctions as well as the corresponding theoretical modeling is briefly summarized. The functions of molecular devices are generally governed by the intrinsic structure-property relationships, and strongly affected by various environment factors including temperature, solvent and intermolecular interactions. Those detailed structural and environmental information could be probed by a powerful tool of inelastic electron tunneling spectroscopy, for which the theoretical modeling becomes particularly important. With many successful examples, it is demonstrated that the combination of theoretical simulations and experimental measurements can help not only to understand the electron-phonon interaction, but more importantly also to accurately determine the real configurations of molecules inside the junctions.
    Keywords: ATK; Application; Review; molecular electronics; single-molecule conductance; self-assembled monolayers; current-voltage characteristics; carbon nanotube electrodes; tunneling spectroscopy; charge-transport; room-temperature; distance-dependence; quantum transport; organic-molecules
    Area: molecular electronics
    BibTeX:
    @article{Lin2013,
      author = {Lin, Lili and Jiang, Jun and Luo, Yi},
      title = {Elastic and inelastic electron transport in metal-molecule(s)-metal junctions},
      journal = {Physica E: Low-dimensional Systems and Nanostructures},
      year = {2013},
      volume = {47},
      number = {0},
      pages = {167--187},
      url = {http://www.sciencedirect.com/science/article/pii/S1386947712004213},
      doi = {http://dx.doi.org/10.1016/j.physe.2012.10.017}
    }
    
    Y.L. Liu, X.Q. Deng & X.C. Duan The electronic transport properties for a single-wall ZnO nanotube with different coupling interfaces 2013 Physica E: Low-dimensional Systems and Nanostructures
    Vol. 52(0), 21-26 
    DOI URL 
    Abstract: The transport properties of a single-wall ZnO nanotube contacted with two Au (Al or Cu ) electrodes are investigated by a theoretical approach. Our results suggest the contact resistance for ZnO nanotube connected with Au electrodes is the largest one as compared with Al and Cu acting as electrodes. The local density of states (LDOS) near the ZnO nanotube/Cu(Al) interface shows the strong electronic interaction. Also shown is that for Au-ZnO system, we can observe a best rectifying performance, the next is the Al-ZnO system, and the third is Cu-ZnO system. This rectification is also fully rationalized by the calculated transmission spectra, the spatial distribution of the lowest unoccupied molecular orbital and highest occupied molecular orbital states, and the electrostatic potential distribution.
    Keywords: ATK; Application; ZnO nanotube; rectification; coupling interface; density functional theory; contact resistance
    Area: nanotubes
    BibTeX:
    @article{Liu2013a,
      author = {Liu, Y.L. and Deng, X.Q. and Duan, X.C.},
      title = {The electronic transport properties for a single-wall ZnO nanotube with different coupling interfaces},
      journal = {Physica E: Low-dimensional Systems and Nanostructures},
      year = {2013},
      volume = {52},
      number = {0},
      pages = {21--26},
      url = {http://www.sciencedirect.com/science/article/pii/S1386947713000817},
      doi = {http://dx.doi.org/10.1016/j.physe.2013.03.016}
    }
    
    Nadine Seidel, Torsten Hahn, Simon Liebing, Wilhelm Seichter, Jens Kortus & Edwin Weber Synthesis and properties of new 9,10-anthraquinone derived compounds for molecular electronics 2013 New J. Chem.
    Vol. 37(3), 601-610 
    DOI  
    Abstract: Fourteen new derivatives of 9,10-anthraquinone or 9,10-dimethoxyanthracene were designed, synthesised and characterised. Regarding the structure, the compounds are [small pi]-conjugated (cross and linear, respectively) and feature thiophene terminated side arms attached to five different positions of the anthraquinone or anthracene core. The synthesis of the compounds involves a cross-coupling procedure in the key reaction steps. Crystal structures of compounds 5 and 19 have been studied. The thiophene containing title compounds 1-5 can be reduced and oxidised by a two step redox process. The electrochemical parameters have been analysed by cyclic voltammetry (CV). Theoretical calculations in the framework of all-electron density functional theory (DFT) were used to investigate the electronic structure of the individual free molecules. Furthermore, calculations of the transport properties of model devices containing compounds 1-3 and respective reduced hydroquinone derivatives assembled at Au(111) electrodes were carried out to evaluate their potential for the application as redox-active switches.
    Keywords: ATK; Application; molecular electronics; alligator clips; electrochemical properties; anion-radicals; anthraquinone; derivatives; dimethylformamide; approximation; intensities; components; efficient
    Area: molecular electronics
    BibTeX:
    @article{Seidel2013,
      author = {Seidel, Nadine and Hahn, Torsten and Liebing, Simon and Seichter, Wilhelm and Kortus, Jens and Weber, Edwin},
      title = {Synthesis and properties of new 9,10-anthraquinone derived compounds for molecular electronics},
      journal = {New J. Chem.},
      publisher = {The Royal Society of Chemistry},
      year = {2013},
      volume = {37},
      number = {3},
      pages = {601--610},
      doi = {http://dx.doi.org/10.1039/C2NJ40772H}
    }
    
    Colin Van Dyck, Victor Geskin, Auke J. Kronemeijer, Dago M. de Leeuw & Jerome Cornil Impact of derivatization on electron transmission through dithienylethene-based photoswitches in molecular junctions 2013 Phys. Chem. Chem. Phys.
    Vol. 15(12), 4392-4404 
    DOI  
    Abstract: We report a combined Non-Equilibrium Green's Function - Density Functional Theory study of molecular junctions made of photochromic diarylethenes between gold electrodes. The impact of derivatization of the molecule on the transmission spectrum is assessed by introducing: (i) substituents on the diarylethene core; and (ii) linker substituents between the gold surface and the diarylethene. We illustrate that substituents on the core shift considerably the HOMO/LUMO level energies in gas phase but do not change the I-V characteristics of the molecular junctions; this behaviour has been rationalized by establishing links between the transmission spectrum and interfacial electronic reorganization upon chemisorption. In contrast, the different linker substituents under study modulate the conductivity of the junction by changing the degree of orbital hybridization with the metallic electrodes and the degree of orbital polarization.
    Keywords: ATK; Application; molecular electronics; generalized gradient approximation; quantum transport; single-molecule; optical-properties; gold electrodes; devices; conductance; diarylethenes; density; isomerization
    Area: molecular electronics
    BibTeX:
    @article{VanDyck2013,
      author = {Van Dyck, Colin and Geskin, Victor and Kronemeijer, Auke J. and de Leeuw, Dago M. and Cornil, Jerome},
      title = {Impact of derivatization on electron transmission through dithienylethene-based photoswitches in molecular junctions},
      journal = {Phys. Chem. Chem. Phys.},
      publisher = {The Royal Society of Chemistry},
      year = {2013},
      volume = {15},
      number = {12},
      pages = {4392--4404},
      doi = {http://dx.doi.org/10.1039/C3CP44132F}
    }
    
    YaQin Wang, YueE. Xie, ZaiLan Zhang, Ye Zhang & YuanPing Chen Spin-polarized transport in zigzag graphene nanoribbons adsorbing nonmagnetic atomic chain 2013 European Physical Journal B
    Vol. 86(2)The European Physical Journal B, 1-6 
    DOI  
    Abstract: The spin-polarized transport properties of nonmagnetic (metallic Al and nonmetallic C) atomic chains adsorbed on zigzag graphene nanoribbons (ZGNRs) are investigated by the density functional theory (DFT) combined with the nonequilibrium Green's function method. We find that the spin polarization of ZGNRs is sensitive to the adsorption sites and atomic types of the chains. As an Al chain is adsorbed on the middle of ZGNR, no spin-polarized transport arises. As the Al chain is adsorbed on the edge of ZGNR, high spin polarization is produced around the Fermi level. The different transport behaviors are originated from the fact that the edge adsorption of Al chain breaks the magnetization symmetry of two edges while the middle adsorption of Al chain only modifies the magnetizations of two edges equally. More prominent spin polarization is generated as a C chain is adsorbed on the edge of ZGNR. The complete spin polarization emerges not only around the Fermi level but also far from the Fermi level, owing to the edge states and the localized states. These results indicate that one can effectively modulate the spin-polarized transports of ZGNRs through adsorbing different nonmagnetic atomic chains.
    Keywords: ATK; Application; graphene nanoribbon; spin; adsorbed atoms; doping; spin-polarized transport
    Area: graphene; spin
    BibTeX:
    @article{Wang2013a,
      author = {Wang, YaQin and Xie, YueE. and Zhang, ZaiLan and Zhang, Ye and Chen, YuanPing},
      title = {Spin-polarized transport in zigzag graphene nanoribbons adsorbing nonmagnetic atomic chain},
      booktitle = {The European Physical Journal B},
      journal = {European Physical Journal B},
      publisher = {Springer-Verlag},
      year = {2013},
      volume = {86},
      number = {2},
      pages = {1-6},
      doi = {http://dx.doi.org/10.1140/epjb/e2012-30912-5}
    }
    
    Huaping Xiao, Chuanxiao Zhang, Kaiwang Zhang, Lizhong Sun & Jianxin Zhong Tunable differential conductance of single wall C/BN nanotube heterostructure 2013 Journal of Molecular Modeling
    Vol. 2013Journal of Molecular Modeling, 1-5 
    DOI  
    Abstract: The transport properties and differential conductance of the heterostructures constructed by (5,5) single wall carbon nanotube (SWCNT) and (5,5) single wall boron nitride nanotube (SWBNNT) are investigated using density functional theory in combination with non-equilibrium Green's functions. We find that the transmission conductance of (5,5) BN/C nanotube heterostructure is not only continually depressed as the BNNT region increases but also the drop of the conductance is uniform in the energy window (-1.43 eV, 1 eV), which leads to linear I-V dependence for the systems when the bias is within this energy range. Moreover, the differential conductance linearly decreases when n<=3 but exponentially decreases when n>=3 for (5,5)(BN) n /C heterostructure. Such tunable differential conductance of (5,5) BN/C nanotube heterostructure mainly derives from the blockage of the transport channels induced by the semiconductive BN segment.
    Keywords: ATK; Application; boron-nitride; C/BN nanotube heterostructure; differential conductance; transport property
    Area: nanotubes
    BibTeX:
    @article{Xiao2013a,
      author = {Xiao, Huaping and Zhang, Chuanxiao and Zhang, Kaiwang and Sun, Lizhong and Zhong, Jianxin},
      title = {Tunable differential conductance of single wall C/BN nanotube heterostructure},
      booktitle = {Journal of Molecular Modeling},
      journal = {Journal of Molecular Modeling},
      publisher = {Springer-Verlag},
      year = {2013},
      volume = {2013},
      pages = {1-5},
      doi = {http://dx.doi.org/10.1007/s00894-013-1823-y}
    }
    
    Chengyu Yang & Quanfang Chen Electronic structure and transport properties of carbon nanotube adsorbed with a copper chain 2013 International Journal of Smart and Nano Materials
    Vol. 2013International Journal of Smart and Nano Materials, 1-7 
    DOI  
    Abstract: The authors have studied the electronic structure and transport properties of hybrid nanowires made of a copper chain adsorbed on a single-wall carbon nanotube (CNT) using first principle methods. Results have shown that after the adsorption of the Cu chain, the density of states and the transmission coefficients of the CNT (5, 5)/Cu nanowire have been increased, while the band gap of CNT (10, 0)/Cu have been significantly reduced. These results imply that the conductivity of CNTs, either metallic or semiconducting, have been enhanced by the adsorption of a copper chain. These hybrid nanowires with enhanced conductivity may be suitable for nanoelectronics.
    Keywords: ATK; Application; nanotubes; atomic chain; nanowire
    Area: nanotubes
    BibTeX:
    @article{Yang2013,
      author = {Yang, Chengyu and Chen, Quanfang},
      title = {Electronic structure and transport properties of carbon nanotube adsorbed with a copper chain},
      booktitle = {International Journal of Smart and Nano Materials},
      journal = {International Journal of Smart and Nano Materials},
      publisher = {Taylor & Francis},
      year = {2013},
      volume = {2013},
      pages = {1--7},
      doi = {http://dx.doi.org/10.1080/19475411.2013.782906}
    }
    
    P. Zhao & D.S. Liu Negative differential resistance behavior in molecular devices based on carbon nanotubes: Effects of chirality and electrode–electrode distance 2013 Physica E: Low-dimensional Systems and Nanostructures
    Vol. 47(0), 224-228 
    DOI URL 
    Abstract: Using first-principles density functional theory and real-space non-equilibrium Green′s function formalism for quantum transport calculation, we investigate all-carbon mechanically controlled molecular devices which consists of only two (5,5) armchair and two (6,0) zigzag single-walled carbon nanotubes (SWCNTs) opposing one another. Our results show that the chirality of SWCNTs and the electrode–electrode distance have crucial effects on the electronic transport properties of such systems. When the right SWCNT electrode is mechanically pushed forward along its axial direction, obvious negative differential resistance behaviors are observed in the zigzag system, but not in the armchair case.
    Keywords: ATK; Application; molecular electronics; transport-properties; field-emission; wire; conductance; junction; graphene; state
    Area: molecular electronics
    BibTeX:
    @article{Zhao2013e,
      author = {Zhao, P. and Liu, D.S.},
      title = {Negative differential resistance behavior in molecular devices based on carbon nanotubes: Effects of chirality and electrode–electrode distance},
      journal = {Physica E: Low-dimensional Systems and Nanostructures},
      year = {2013},
      volume = {47},
      number = {0},
      pages = {224--228},
      url = {http://www.sciencedirect.com/science/article/pii/S1386947712004493},
      doi = {http://dx.doi.org/10.1016/j.physe.2012.11.008}
    }
    
    Vladimir Kolchuzhin, Jan Mehner, Milind Shende, Erik Markert, Ulrich Heinkel, Christian Wagner & Thomas Gessner System Level Modelling of CNT based Mechanical Sensor 2013 Chemnitzer Fachtagung Mikrosystemtechnik
    Vol. 11, 1-6 
    URL 
    Abstract: This article presents a system level model of carbon nanotube (CNT) based mechanical sensor, which consists of micro-electro-mechanical (MEMS) platform that is served to actuate single-axis force and single CNT is placed between the movable and fixed electrodes. The change in conductivity of CNT, when strain is applied, is used to measure force or displacement. The simulation of the whole sensor element will be achieved by using the framework of hardware description languages (VHDL-AMS and SystemC-AMS) that uses compact models to describe sub-elements performing heterogeneous functions. The CNT piezoresistive compact model presented in the article is based on the analytical model and the simulations results from density functional theory (DFT). The macromodel of the MEMS platform is build using mode superposition technique. The results of the system simulations are presented and discussed in the article.
    Keywords: ATK; Application; nanotube; piezoelectric effect; mechanical sensor; compact model; DFT;
    Area: nanotubes
    BibTeX:
    @article{Kolchuzhin2013,
      author = {Kolchuzhin, Vladimir and Mehner, Jan and Shende, Milind and Markert, Erik and Heinkel, Ulrich and Wagner, Christian and Gessner, Thomas},
      title = {System Level Modelling of CNT based Mechanical Sensor},
      journal = {Chemnitzer Fachtagung Mikrosystemtechnik},
      year = {2013},
      volume = {11},
      pages = {1-6},
      url = {http://www.researchgate.net/publication/235338375_System_Level_Modelling_of_CNT_based_Mechanical_Sensor/file/32bfe5110c3b56b43e.pdf}
    }
    
    Yukihito Matsuura & Toshifumi Morioka Quantum Transport in mu-Cyclopentadienyl Indium Complex 2013 Molecular Crystals and Liquid Crystals
    Vol. 574(1)Molecular Crystals and Liquid Crystals, 135-142 
    DOI  
    Abstract: The electronic structure and conductance of a mu-cyclopentadienyl indium (Cp-In) multidecker complex have been examined by using the density functional theory (DFT). The electrical conduction of the complex between gold electrodes is investigated by using Green's function formalism. The one-dimensional band structure exhibited semiconducting properties. The Cp5In4- complex, which had a long molecular length, between gold electrodes, exhibited low electrical conduction. On the other hand, the Cp3In2- complex between the gold electrodes had transmission at the Fermi level. The I-V curves suggest the intrinsic characteristics of semiconducting properties and the suppression of strong tunneling effect.
    Keywords: ATK; Application; molecular electronics
    Area: molecular electronics
    BibTeX:
    @article{Matsuura2013a,
      author = {Matsuura, Yukihito and Morioka, Toshifumi},
      title = {Quantum Transport in mu-Cyclopentadienyl Indium Complex},
      booktitle = {Molecular Crystals and Liquid Crystals},
      journal = {Molecular Crystals and Liquid Crystals},
      publisher = {Taylor & Francis},
      year = {2013},
      volume = {574},
      number = {1},
      pages = {135--142},
      doi = {http://dx.doi.org/10.1080/15421406.2012.763016}
    }
    
    Xiaozan Wu, Guanghui Huang, Qingbin Tao & Hui Xu Effect of boron/nitrogen codoping on transport properties of C60 molecular devices 2013 J. Cent. South Univ.
    Vol. 20, 889-893 
    DOI  
    Abstract: By using nonequilibrium Green's function method and firstprinciples calculations, the electronic transport properties of doped C60 molecular devices were investigated. It is revealed that the C60 molecular devices show the metal behavior due to the interaction between the C60 molecule and the metal electrode. The current-voltage curve displays a linear behavior at low bias, and the currents have the relation of M1>M3>M4>M2 when the bias voltage is lower than 0.6 V. Electronic transport properties are affected greatly by the doped atoms. Negative differential resistance is found in a certain bias range for C60 and C58BN molecular devices, but cannot be observed in C59B and C59N molecular devices. These unconventional effects can be used to design novel nanoelectronic devices.
    Keywords: ATK; Application; negative differential resistance; molecular device; electronic transport property; first-principles calculation
    Area: molecular electronics
    BibTeX:
    @article{Wu2013a,
      author = {Wu, Xiaozan and Huang, Guanghui and Tao, Qingbin and Xu, Hui},
      title = {Effect of boron/nitrogen codoping on transport properties of C60 molecular devices},
      journal = {J. Cent. South Univ.},
      year = {2013},
      volume = {20},
      pages = {889-893},
      doi = {http://dx.doi.org/10.1007/s11771-013-1562-3}
    }
    
    P. Zhao, D.S. Liu, S.J. Li & G. Chen Modulation of rectification and negative differential resistance in graphene nanoribbon by nitrogen doping 2013 Physics Letters A
    Vol. 377(15), 1134-1138 
    DOI  
    Abstract: Abstract By applying the nonequilibrium Green's function formalism combined with density functional theory, we have investigated the electronic transport properties of two nitrogen-doped armchair graphene nanoribbon-based junctions M1 and M2. In the left part of M1 and M2, nitrogen atoms are doped at two edges of the nanoribbon. In the right part, nitrogen atoms are doped at one edge and at the center for M1 and M2, respectively. Obvious rectifying and negative differential resistance behaviors are found, which are strongly dependent on the doping position. The maximum rectification and peak-to-valley ratios are up to the order of 10^4 in M2.
    Keywords: ATK; Application; graphene nanoribbon; electronic transport; rectification; negative differential resistance; NDR;
    Area: graphene
    BibTeX:
    @article{Zhao2013b,
      author = {Zhao, P. and Liu, D.S. and Li, S.J. and Chen, G.},
      title = {Modulation of rectification and negative differential resistance in graphene nanoribbon by nitrogen doping},
      journal = {Physics Letters A},
      year = {2013},
      volume = {377},
      number = {15},
      pages = {1134--1138},
      doi = {http://dx.doi.org/10.1016/j.physleta.2013.02.048}
    }
    
    JingFen Zhao, ChuanLu Yang, MeiShan Wang & Jie Ma First-principles analysis of the effect of contact sites on electronic transport properties of diaminofluorene 2013 Physica B: Condensed Matter
    Vol. 417(0), 70-74 
    DOI  
    Abstract: The effects of atop, hollow, bridge and adatom contact sites on the electronic transport properties of a single diaminofluorene molecule connected to gold electrodes are studied by using nonequilibrium Green's functions in combination with the density functional theory. Computational results were analyzed to identify the contact site utilized in the experiment of Lu et al. (2009) [26]. Current-voltage curves were also examined. The rectifying behavior of diaminofluorene was observed in the atop, hollow and bridge contact sites. The highest occupied molecular orbital, the lowest unoccupied molecular orbital and transmission spectra were used in determining the various electronic transport properties of diaminofluorene.
    Keywords: ATK; Application; rectifying behavior; contact sites; nonequilibrium Green's function; density functional theory; electronic transport; molecular electronics
    Area: molecular electronics
    BibTeX:
    @article{Zhao2013c,
      author = {Zhao, JingFen and Yang, ChuanLu and Wang, MeiShan and Ma, Jie},
      title = {First-principles analysis of the effect of contact sites on electronic transport properties of diaminofluorene},
      journal = {Physica B: Condensed Matter},
      year = {2013},
      volume = {417},
      number = {0},
      pages = {70--74},
      doi = {http://dx.doi.org/10.1016/j.physb.2013.02.007}
    }
    
    P. Zhao, D.S. Liu & G. Chen Effect of mono-vacancy on transport properties of zigzag carbon- and boron-nitride-nanotube heterostructures 2013 Solid State Communications
    Vol. 160(0), 13-16 
    DOI  
    Abstract: On the basis of first-principles density functional theory and non-equilibrium Green's function technique, we have investigated the effects of a mono-vacancy on the electronic transport properties of the carbon nanotube/boron nitride nanotube heterostructures. The results show that the electronic transport properties are strongly dependent on the position of the mono-vacancy, and the negative differential resistance and rectifying performances can be strengthened or weakened alternately with the position change of the mono-vacancy. Moreover, the performance change is more significant when the mono-vacancy occurs on the carbon nanotube part. These interesting phenomena are explained in terms of the evolution of the transmission spectrum with applied bias combined with molecular projected self-consistent Hamiltonian states analysis.
    Keywords: ATK; Application; boron-nitride; nanotube; vacancy electronic transport; negative differential resistance; rectifying; molecular electronics
    Area: nanotubes
    BibTeX:
    @article{Zhao2013d,
      author = {Zhao, P. and Liu, D.S. and Chen, G.},
      title = {Effect of mono-vacancy on transport properties of zigzag carbon- and boron-nitride-nanotube heterostructures},
      journal = {Solid State Communications},
      year = {2013},
      volume = {160},
      number = {0},
      pages = {13--16},
      doi = {http://dx.doi.org/10.1016/j.ssc.2013.02.007}
    }
    
    Bagavathi Chandrasekara Nanotransistors from metal and metalloid compound nanotubes 2013 International Journal of Scientific & Engineering Research
    Vol. 4(2), 1-4 
    URL 
    Abstract: The escalating trend of chip integration and miniaturization has dared the designers to seek to a nascent phenomenon to save the Moore's law. Due to continuous reduction in device size, the so-far-unseen quantum effects have dominated the device physics. The solution to this crisis is nanoelectronics. Nano structures are used to develop new devices by utilizing the quantum effects. III group compounds have been known for their special properties as semiconductors in electronics. By including nanoscale nature with III group compounds, greater advantages can be obtained. III group nitride nanotubes have been investigated in many works. The nanotubes under discussion are boron nitride nanotubes and gallium nitride nanotubes. The phenomenon used for analysis in this work is Density Functional Theory (DFT). The characteristics of a device can be deduced from the electronic cloud structure around the device through density functional theory. In this work, III group nitride nanotubes are employed as transistor channels and their characteristics are scrutinized through simulation studies.
    Keywords: ATK; Application; transistor; boron-nitride; nanotube; gallium nitride; nanotube transistor; third group nanotubes; density functional theory; simulation of nanomaterials
    Area: nanotubes
    BibTeX:
    @article{Chandrasekara2013,
      author = {Bagavathi Chandrasekara},
      title = {Nanotransistors from metal and metalloid compound nanotubes},
      journal = {International Journal of Scientific & Engineering Research},
      year = {2013},
      volume = {4},
      number = {2},
      pages = {1-4},
      url = {http://www.ijser.org/researchpaper/NANOTRANSISTORS-FROM-METAL-AND-METALLOID-COMPOUND-NANOTUBES.pdf}
    }
    
    Pengwei Li, Zhi Yang, Wendong Zhang & Shijie Xiong The magnetic properties and spin-filter effects of manganese-borazine sandwich clusters 2013 Journal of Molecular Structure
    Vol. 1038(0), 1-7 
    DOI  
    Abstract: In present paper, detailed investigations on the magnetic and quantum transport properties of Mn_n(B_3N_3H_6)_n+1 (n = 1-4) sandwich clusters were performed by using density functional theory and non-equilibrium Green's function technique. The calculated results show that these clusters are stable and adopt ferromagnetic orders as the ground states. When coupled to Ni electrodes, the sandwiches could exhibit novel quantum transport properties such as high spin-filter capabilities and negative differential resistance effects, indicating that these sandwich systems could be viewed as a new kind of spin filter.
    Keywords: ATK; Application; molecular electronics; sandwich; cluster; spin filter
    Area: molecular electronics; spin
    BibTeX:
    @article{Li2013a,
      author = {Li, Pengwei and Yang, Zhi and Zhang, Wendong and Xiong, Shijie},
      title = {The magnetic properties and spin-filter effects of manganese-borazine sandwich clusters},
      journal = {Journal of Molecular Structure},
      year = {2013},
      volume = {1038},
      number = {0},
      pages = {1--7},
      doi = {http://dx.doi.org/10.1016/j.molstruc.2013.01.022}
    }
    
    Qing-Qing Sun, Yong-Jun Li, Jin-Lan He, Wen Yang, Peng Zhou, Hong-Liang Lu, Shi-Jing Ding & David Wei Zhang The physics and backward diode behavior of heavily doped single layer MoS2 based p-n junctions 2013 Applied Physics Letters
    Vol. 102(9), 093104 
    DOI  
    Abstract: The single layer MoS2 is attractive for the use in the next-generation low power nanoelectronic devices because of its intrinsic bandgap compared to graphene. In this work, we investigated the transport property of a p-n junction based on two-dimensional MoS2. The n-type and p-type doping are realized through substituting sulfur with chlorine and phosphorus. The device exhibited backward diode-like behavior with large rectifying ratios. We attribute the observed current-voltage characteristics to different heavy doping effect caused by chlorine and phosphorus. Our results may throw light on the electronic modulation of MoS2 and realizations of complemented logics devices based on MoS2.
    Keywords: ATK; Application; MoS2; p-n junction; diodes; energy gap; molybdenum compounds; rectification; transistors; graphene
    Area: graphene; dichalcogenides
    BibTeX:
    @article{Sun2013,
      author = {Sun, Qing-Qing and Li, Yong-Jun and He, Jin-Lan and Yang, Wen and Zhou, Peng and Lu, Hong-Liang and Ding, Shi-Jing and Zhang, David Wei},
      title = {The physics and backward diode behavior of heavily doped single layer MoS2 based p-n junctions},
      journal = {Applied Physics Letters},
      publisher = {AIP},
      year = {2013},
      volume = {102},
      number = {9},
      pages = {093104},
      doi = {http://dx.doi.org/10.1063/1.4794802}
    }
    
    Fang Wang, Yonglai Zhang, Yang Liu, Xuefeng Wang, Mingrong Shen, Shuit-Tong Lee & Zhenhui Kang Opto-electronic conversion logic behaviour through dynamic modulation of electron/energy transfer states at the TiO2-carbon quantum dot interface 2013 Nanoscale
    Vol. 5(5), 1831-1835 
    DOI  
    Abstract: Here we show a bias-mediated electron/energy transfer process at the CQDs-TiO2 interface for the dynamic modulation of opto-electronic properties. Different energy and electron transfer states have been observed in the CQDs-TNTs system due to the up-conversion photoluminescence and the electron donation/acceptance properties of the CQDs decorated on TNTs.
    Keywords: ATK; Application; TiO2 nanotube; phonons; photoluminescence; optoelectronics; doping; visible-light; carbon; photocatalyst; nanotubes; circuits
    Area: nanotubes
    BibTeX:
    @article{Wang2013,
      author = {Wang, Fang and Zhang, Yonglai and Liu, Yang and Wang, Xuefeng and Shen, Mingrong and Lee, Shuit-Tong and Kang, Zhenhui},
      title = {Opto-electronic conversion logic behaviour through dynamic modulation of electron/energy transfer states at the TiO2-carbon quantum dot interface},
      journal = {Nanoscale},
      publisher = {The Royal Society of Chemistry},
      year = {2013},
      volume = {5},
      number = {5},
      pages = {1831--1835},
      doi = {http://dx.doi.org/10.1039/C3NR33985H}
    }
    
    H.P. Xiao, Chaoyu He, C.X. Zhang, L.Z. Sun, Pan Zhou & Jianxin Zhong Stability, electronic structures and transport properties of armchair (10, 10) BN/C nanotubes 2013 Journal of Solid State Chemistry
    Vol. 200(0), 294-298 
    DOI URL 
    Abstract: Using the first-principle calculations, the stability and electronic properties of two novel types of four-segment armchair (10, 10) BN/C hybrid nanotubes ((BN)5C5(BN)5C5NT and (BN)5C5(NB)5C5NT) as well as two-segment armchair (10, 10) BN/C hybrid nanotubes ( ( BN 20-n C n NTs ) are systematically investigated. When n increases from 1 to 4, the band gap of ( BN ) 20-n C n NTs gradually decreases to a narrow one. When 4<=n<=17 , the electronic structure of carbon segment in ( BN ) 20-n C n NTs behaves as zigzag graphene nanoribbons whose band gap is modulated by an inherent electric field of the BN segment. ZGNR-like segments in (BN)5C5(BN)5C5NT and (BN)5C5(NB)5C5NT behave as narrow gap semiconductor and metal, respectively, due to their different chemical environment. Moreover, the (BN)5C5(NB)5C5NT can separate electron and hole carriers, indicating its potential application in solar cell materials. Obvious transport enhancement around the Fermi level is found in the four-segment nanotubes, especially a 6G0 transmission peak in the metallic (BN)5C5(NB)5C5NT.
    Keywords: ATK; Application; boron-nitride carbon hybrid nanotubes; density functional theory; non-equilibrium Green's function; electronic properties; transport properties
    Area: nanotubes
    BibTeX:
    @article{Xiao2013,
      author = {Xiao, H.P. and He, Chaoyu and Zhang, C.X. and Sun, L.Z. and Zhou, Pan and Zhong, Jianxin},
      title = {Stability, electronic structures and transport properties of armchair (10, 10) BN/C nanotubes},
      journal = {Journal of Solid State Chemistry},
      year = {2013},
      volume = {200},
      number = {0},
      pages = {294--298},
      url = {http://www.sciencedirect.com/science/article/pii/S002245961300042X},
      doi = {http://dx.doi.org/10.1016/j.jssc.2013.01.026}
    }
    
    Peng Zhao, De-Sheng Liu, Hai-Ying Liu, Shu-Juan Li & Gang Chen Low bias negative differential resistance in C60 dimer modulated by gate voltage 2013 Organic Electronics
    Vol. 14(4), 1109-1115 
    DOI URL 
    Abstract: By using a combined method of density functional theory and nonequilibrium Green's function formalism, we investigate the electronic transport properties of a gated C60 dimer molecule sandwiched between two gold electrodes. The results show that the gate voltage can strongly affect the electronic transport properties of the C60 dimer and change it from semiconducting to metallic. Negative differential resistance behaviors are obtained in such systems and can be modulated to occur at much lower bias by the gate voltage. The low bias negative differential resistance is analyzed from the calculated transmission spectra, projected density of states and the spatial distribution of molecular projected self-consistent Hamiltonian orbitals along with the voltage drop. These results provide a theoretical support to the design of low bias negative differential resistance molecular device by using the modulation of gate voltage.
    Keywords: ATK; Application; fullerene; electronic transport; negative differential resistance; NDR;
    Area: molecular electronics; fullerenes
    BibTeX:
    @article{Zhao2013a,
      author = {Zhao, Peng and Liu, De-Sheng and Liu, Hai-Ying and Li, Shu-Juan and Chen, Gang},
      title = {Low bias negative differential resistance in C60 dimer modulated by gate voltage},
      journal = {Organic Electronics},
      year = {2013},
      volume = {14},
      number = {4},
      pages = {1109--1115},
      url = {http://www.sciencedirect.com/science/article/pii/S1566119913000529},
      doi = {http://dx.doi.org/10.1016/j.orgel.2013.01.034}
    }
    
    Jiaping Fan, Nahashon Ndegwa Gathitu, Yingfei Chang & Jingping Zhang Effect of length on the position of negative differential resistance and realization of multifunction in fused oligothiophenes based molecular device 2013 The Journal of Chemical Physics
    Vol. 138(7), 074307 
    DOI  
    Abstract: The length modulation of electron transport properties for molecular devices based on fused oligothiophenes has been investigated theoretically using a combination of non-equilibrium Green's functions and first-principles density functional theory. The results show that the lengths of the molecules have a distinct influence on the position of negative differential resistance (NDR) of the molecular devices. By exploring the effect on transmission properties of substituent groups, hexathieno[3,2-b:2',3'-d]thiophene with -NH2 and -NO2 substituents (model L) can be regard as a good candidate of multifunctional molecular device, which shows excellent rectifying performance (the largest rectification ration is 14.3 at 1.2 V) and clear NDR behavior (at 1.4 V).
    Keywords: ATK; Application; electric properties; Green's function methods; molecular electronics; nanoelectronics; nitrogen compounds; organic compounds; ab-initio; 1st-principles; conductance; contact; transport; junction
    Area: molecular electronics
    BibTeX:
    @article{Fan2013,
      author = {Fan, Jiaping and Gathitu, Nahashon Ndegwa and Chang, Yingfei and Zhang, Jingping},
      title = {Effect of length on the position of negative differential resistance and realization of multifunction in fused oligothiophenes based molecular device},
      journal = {The Journal of Chemical Physics},
      publisher = {AIP},
      year = {2013},
      volume = {138},
      number = {7},
      pages = {074307},
      doi = {http://dx.doi.org/10.1063/1.4790805}
    }
    
    Zhi-Qiang Fan, Zhen-Hua Zhang, Xiao-Qing Deng, Gui-Ping Tang & Ke-Qiu Chen Controllable low-bias negative differential resistance and rectifying behaviors induced by symmetry breaking 2013 Applied Physics Letters
    Vol. 102(2), 023508 
    DOI  
    Abstract: Incorporating the characteristic of pyramidal electrode and symmetry breaking of molecular structure, we theoretically design a molecular device to perform negative differential resistance and rectifying behaviors simultaneously. The calculated results reveal that low-bias negative differential resistance behaviors can appear symmetrically when tetraphenyl molecule connects to pyramidal gold electrodes. However, as one phenyl of tetraphenyl molecule is replaced by a pyrimidyl, the symmetry breaking on the molecule will break the symmetry of negative differential resistance behavior. The peak-to-valley ratio on negative bias region is larger than that on positive bias region to perform a low-bias rectifying behavior. More importantly, increasing the symmetry breaking can further weaken these two behaviors which propose an effective way to modulate them.
    Keywords: ATK; Application; gold; metal-insulator boundaries; molecular electronics; negative resistance; organic compounds; rectification; molecular rectifiers; atomic-scale device; junction; diode
    Area: molecular electronics
    BibTeX:
    @article{Fan2013a,
      author = {Fan, Zhi-Qiang and Zhang, Zhen-Hua and Deng, Xiao-Qing and Tang, Gui-Ping and Chen, Ke-Qiu},
      title = {Controllable low-bias negative differential resistance and rectifying behaviors induced by symmetry breaking},
      journal = {Applied Physics Letters},
      publisher = {AIP},
      year = {2013},
      volume = {102},
      number = {2},
      pages = {023508},
      doi = {http://dx.doi.org/10.1063/1.4788691}
    }
    
    Afif Gouissem, Wu Fan, Adri C.T. van Duin & Pradeep Sharma A reactive force-field for Zirconium and Hafnium Di-Boride 2013 Computational Materials Science
    Vol. 70(0), 171-177 
    DOI  
    Abstract: Zirconium and Hafnium Di-Boride are the two major material systems that are of critical importance for applications in ultra-high temperature environments where both oxidation and mechanical damage mechanisms (such as creep) are operative. Atomistic simulations of these materials at finite temperatures have been hampered due to the unavailability of inter-atomic potentials for the involved elements. In this paper, we present the development of interatomic potentials for both ZrB2 and HfB2 within the ReaxFF framework, thus enabling modeling of chemical reactions. The parameters of the reactive force field are derived by fitting to detailed quantum mechanical simulations of ZrB2 and HfB2 clusters and crystal structures.
    Keywords: ATK; Application; interatomic force-field; chemical reactions; high temperature materials; reaxFF; fitting
    Area: semi
    BibTeX:
    @article{Gouissem2013,
      author = {Gouissem, Afif and Fan, Wu and van Duin, Adri C.T. and Sharma, Pradeep},
      title = {A reactive force-field for Zirconium and Hafnium Di-Boride},
      journal = {Computational Materials Science},
      year = {2013},
      volume = {70},
      number = {0},
      pages = {171--177},
      doi = {http://dx.doi.org/j.commatsci.2012.12.038}
    }
    
    Jing Huang, Qunxiang Li & Jinlong Yang Tuning the Electronic Properties of N@C60 Molecule: A Theoretical Study 2013 Journal of Nanoscience and Nanotechnology
    Vol. 13(2), 1053-1058 
    DOI  
    Abstract: We used first-principle calculations to explore the electronic and transport properties of N@C60 molecule. The calculated results indicate that the N atom locates at either slight or significant off-center in C60 cage under various different chemical environments. The localized N atomic magnetic moment in N@C60 molecule is about 3.0 muB, which is not sensitive to the chemical environment, such as the carrier doping, the external electric field, and the molecule-substrate interaction. On the other hand, the magnetism of N@C60 can be effectively tuned by carrier doping and the cage chemical modification. The C60 cage with delocalized pi-electrons character demonstrates a significant shielding (about 80%) of the encapsulated N atom from the applied external electric field. We do not observe obvious transmission spin polarization in N@C60 molecular junctions and the transmission spectra of two spin channels are similar near the Fermi level.
    Keywords: ATK; Application; molecular electronics; fullerenes
    Area: molecular electronics; fullerenes
    BibTeX:
    @article{Huang2013,
      author = {Huang, Jing and Li, Qunxiang and Yang, Jinlong},
      title = {Tuning the Electronic Properties of N@C60 Molecule: A Theoretical Study},
      journal = {Journal of Nanoscience and Nanotechnology},
      year = {2013},
      volume = {13},
      number = {2},
      pages = {1053--1058},
      doi = {http://dx.doi.org/10.1166/jnn.2013.6116}
    }
    
    Anurag Srivastava, B. Santhibhushan & Pankaj Dobwal Performance analysis of impurity added benzene based single-electron transistor 2013 Appl. Nanosci.
    Vol. 2Applied Nanoscience, 1-7 
    DOI  
    Abstract: We have analyzed the impurity added benzene based single-electron transistor (SET) using the ab initio approach, based on density functional theory and non-equilibrium Green's function. Boron and nitrogen has been added as impurities either by replacing the last carbon atom or last hydrogen in the benzene. The system has been modeled in such a way that the impurity added benzene is placed above the gate dielectric in coulomb blockade regime between source and drain electrodes for weak coupling. The charging energies of the system have been calculated and discussed in both the isolated as well as SET environments. The conductance dependence of SET on bias potential and gate voltage has been verified through charge stability diagrams.
    Keywords: ATK; Application; impurity added benzene (IAB); single-electron transistor (SET); Charge states, Charging energy, Charge stability diagram
    Area: SET
    BibTeX:
    @article{Srivastava2013,
      author = {Srivastava, Anurag and Santhibhushan, B. and Dobwal, Pankaj},
      title = {Performance analysis of impurity added benzene based single-electron transistor},
      booktitle = {Applied Nanoscience},
      journal = {Appl. Nanosci.},
      publisher = {Springer-Verlag},
      year = {2013},
      volume = {2},
      pages = {1-7},
      doi = {http://dx.doi.org/10.1007/s13204-013-0194-0}
    }
    
    F. Tavazza, S. Barzilai, D.T. Smith & L.E. Levine The increase in conductance of a gold single atom chain during elastic elongation 2013 Journal of Applied Physics
    Vol. 113(5), 054316 
    DOI  
    Abstract: The conductance of monoatomic gold wires has been studied using ab initio calculations and the transmission was found to vary with the elastic strain. Counter-intuitively, the conductance was found to increase for the initial stages of the elongation, where the structure has a zigzag shape and the bond angles increase from 140° toward 160°. After a certain elongation limit, where the angles are relatively high, the bond length elongation associated with a Peierls distortion reverses this trend and the conductance decreases. These simulations are in good agreement with previously unexplained experimental results.
    Keywords: ATK; Application; nanowire; conductance quantization; elastic properties; plasticity; ab initio calculations; bond angles; bond lengths; elasticity, electrical conductivity; elongation; gold; geometry optimization; transport; molecules; geometry optimization; transport; molecules
    Area: nanowires
    BibTeX:
    @article{Tavazza2013,
      author = {Tavazza, F. and Barzilai, S. and Smith, D. T. and Levine, L. E.},
      title = {The increase in conductance of a gold single atom chain during elastic elongation},
      journal = {Journal of Applied Physics},
      publisher = {AIP},
      year = {2013},
      volume = {113},
      number = {5},
      pages = {054316},
      doi = {http://dx.doi.org/10.1063/1.4790379}
    }
    
    Jiaxin Zheng, Lu Wang, Ruge Quhe, Qihang Liu, Hong Li, Dapeng Yu, Wai-Ning Mei, Junjie Shi, Zhengxiang Gao & Jing Lu Sub-10 nm Gate Length Graphene Transistors: Operating at Terahertz Frequencies with Current Saturation 2013 Sci. Rep.
    Vol. 3, 1314 
    DOI  
    Abstract: Radio-frequency application of graphene transistors is attracting much recent attention due to the high carrier mobility of graphene. The measured intrinsic cut-off frequency (fT) of graphene transistor generally increases with the reduced gate length (Lgate) till Lgate = 40 nm, and the maximum measured fT has reached 300 GHz. Using ab initio quantum transport simulation, we reveal for the first time that fT of a graphene transistor still increases with the reduced Lgate when Lgate scales down to a few nm and reaches astonishing a few tens of THz. We observe a clear drain current saturation when a band gap is opened in graphene, with the maximum intrinsic voltage gain increased by a factor of 20. Our simulation strongly suggests it is possible to design a graphene transistor with an extraordinary high fT and drain current saturation by continuously shortening Lgate and opening a band gap.
    Keywords: ATK; Application; graphene; scaling laws; applied physics; electronic properties and devices; nanosensors; radio frequency applications; field-effect transistors; walled carbon nanotubes; epitaxial graphene; bilayer graphene; room-temperature; tunable bandgap; boron-nitride; ab-initio; transport; devices
    Area: graphene
    BibTeX:
    @article{Zheng2013a,
      author = {Zheng, Jiaxin and Wang, Lu and Quhe, Ruge and Liu, Qihang and Li, Hong and Yu, Dapeng and Mei, Wai-Ning and Shi, Junjie and Gao, Zhengxiang and Lu, Jing},
      title = {Sub-10 nm Gate Length Graphene Transistors: Operating at Terahertz Frequencies with Current Saturation},
      journal = {Sci. Rep.},
      publisher = {Macmillan Publishers Limited. All rights reserved},
      year = {2013},
      volume = {3},
      pages = {1314},
      doi = {http://dx.doi.org/10.1038/srep01314}
    }
    
    Zhaoqiang Bai, Lei Shen, Qingyun Wu, Minggang Zeng, Jian-Sheng Wang, Guchang Han & Yuan Ping Feng Boron diffusion induced symmetry reduction and scattering in CoFeB/MgO/CoFeB magnetic tunnel junctions 2013 Physical Review B
    Vol. 87(1), 014114- 
    DOI  
    Abstract: By first-principles analysis, we investigate the effect of thermal annealing on structural stability of CoFeB/MgO(thin)/CoFeB magnetic tunnel junctions. The calculated phonon dispersion indicates that Mg3B2O6 (kotoite) is a stable spacer after annealing due to B diffusion into MgO. The calculated tunneling magnetoresistance (TMR) of CoFe/kotoite/CoFe is 210%, which is in good agreement with the available experimental value and 2 orders of magnitude lower than the predicted values of CoFe/MgO/CoFe junctions. The physics of this more realistic TMR value is the change in symmetry from C4v of MgO to C2v of kotoite. Such symmetry reduction induces scattering and weakens the tunneling transmission of the &Delta;1-like Bloch states. Our calculations also reveal that the tunneling transmission is sensitive to the electrode/spacer interfacial chemical bonding. Residual boron, localized at the interface due to insufficient annealing temperature, can further reduce the TMR.
    Keywords: ATK; Application; magnetic tunnel junction; spin; MTJ; diffusion; boron; room-temperature; magnetoresistance; complex bandstructure; transmission eigenstates; transmission pathways;
    Area: interfaces; spin; semi; nvm
    BibTeX:
    @article{Bai2013,
      author = {Bai, Zhaoqiang and Shen, Lei and Wu, Qingyun and Zeng, Minggang and Wang, Jian-Sheng and Han, Guchang and Feng, Yuan Ping},
      title = {Boron diffusion induced symmetry reduction and scattering in CoFeB/MgO/CoFeB magnetic tunnel junctions},
      journal = {Physical Review B},
      publisher = {American Physical Society},
      year = {2013},
      volume = {87},
      number = {1},
      pages = {014114--},
      doi = {http://dx.doi.org/10.1103/PhysRevB.87.014114}
    }
    
    Satyendra Singh Chauhan, Pankaj Srivastava & A.K. Shrivastava Effect of Vacancy on Electronic and Transport Properties of Graphene Nanoribbons: An Ab Initio Approach 2012 Journal of Computational and Theoretical Nanoscience
    Vol. 9(12), 2215-2216 
    DOI  
    Abstract: We report a spin-unpolarized density functional theory study of electronic and transport properties of zigzag graphene nanoribbons (ZGNRs) defected with one and two vacancy atoms. The pristine and vacancy defected structures of 8 ZGNRs are found to be metallic. The one atom vacancy ZGNRs is energetically more stable. The localized states appear when there are vacancies inside the ZGNRs, which affects its transmission. In case of two vacancies in the ZGNRs the additional peak in DOS is observed close to the Fermi level and the transmission decreases further. Hence, our results point towards the relative suitability of these materials in nanoelectronics applications.
    Keywords: ATK; Application; graphene nanoribbons; stability; electronic; transport; metallic; defect
    Area: graphene
    BibTeX:
    @article{Chauhan2012a,
      author = {Chauhan, Satyendra Singh and Srivastava, Pankaj and Shrivastava, A.K.},
      title = {Effect of Vacancy on Electronic and Transport Properties of Graphene Nanoribbons: An Ab Initio Approach},
      journal = {Journal of Computational and Theoretical Nanoscience},
      year = {2012},
      volume = {9},
      number = {12},
      pages = {2215--2216},
      doi = {http://dx.doi.org/10.1166/jctn.2012.2641}
    }
    
    Ming-Jun Li, Meng-Qiu Long, Ke-Qiu Chen & Hui Xu Fluorination effects on the electronic transport properties of dithiophene-tetrathiafulvalene (DT-TTF) molecular junctions 2013 Solid State Communications
    Vol. 157(0), 62-67 
    DOI  
    Abstract: The fluorination of dithiophene-tetrathiafulvalent (DT-TTF) was investigated by using the density functional theory combined with nonequilibrium Green's function method. It is demonstrated that fluorination can modify the electronic transport properties of DT-TTF. Negative differential resistance can be observed within a certain bias voltage range in 4FDT-TTF.
    Keywords: ATK; Application; molecular electronics; dithiophene-tetrathiafulvalene; fluorination effect; transport property; NDR behavior; negative differential resistance; field-effect transistors; intermolecular interaction; high-performance; high-mobility; metal-ions; ab-initio; devices; 1st-principles; wires
    Area: molecular electronics
    BibTeX:
    @article{Li2013,
      author = {Li, Ming-Jun and Long, Meng-Qiu and Chen, Ke-Qiu and Xu, Hui},
      title = {Fluorination effects on the electronic transport properties of dithiophene-tetrathiafulvalene (DT-TTF) molecular junctions},
      journal = {Solid State Communications},
      year = {2013},
      volume = {157},
      number = {0},
      pages = {62--67},
      doi = {http://dx.doi.org/10.1016/j.ssc.2012.12.001}
    }
    
    Hongmei Liu, Hongbo Wang, Jianwei Zhao & Manabu Kiguchi Molecular rectification in triangularly shaped graphene nanoribbons 2013 J. Comput. Chem.
    Vol. 34(5), 360-365 
    DOI  
    Abstract: We present a theoretical study of electron transport in tailored zigzag graphene nanoribbons (ZGNRs) with triangular structure using density functional theory together with the nonequilibrium Green's function formalism. We find significant rectification with a favorite electron transfer direction from the vertex to the right edge. The triangular ZGNR connecting to the electrode with one thiol group at each terminal shows an average rectification ratio of 8.4 over the bias range from -1.0 to 1.0 V. This asymmetric electron transport property originates from nearly zero band gap of triangular ZGNR under negative bias, whereas a band gap opens under positive bias. When the molecule is connected to the electrode by multithiol groups, the current is enhanced due to strong interfacial coupling; however, the rectification ratio decreases. The simulation results indicate that the unique electronic states of triangular ZGNR are responsible for rectification, rather than the asymmetric anchoring groups.
    Keywords: ATK; Application; triangular graphene nanoribbon; molecular rectification; band gap; electron transport; quantum-interference; electron-transport; wire junctions; conductance; resistance; nanodisk; contact; formula
    Area: graphene
    BibTeX:
    @article{Liu2013,
      author = {Liu, Hongmei and Wang, Hongbo and Zhao, Jianwei and Kiguchi, Manabu},
      title = {Molecular rectification in triangularly shaped graphene nanoribbons},
      journal = {J. Comput. Chem.},
      publisher = {Wiley Subscription Services, Inc., A Wiley Company},
      year = {2013},
      volume = {34},
      number = {5},
      pages = {360--365},
      doi = {http://dx.doi.org/10.1002/jcc.23142}
    }
    
    M. Qiu & K.M. Liew Length dependence of carbon-doped BN nanowires: A-D Rectification and a route to potential molecular devices 2013 Journal of Applied Physics
    Vol. 113(5), 054305 
    DOI  
    Abstract: Based on the first-principles approach, electronic transport properties of different lengths of carbon-doped boron-nitrogen nanowires, capped with two thiols as end groups connected to Au electrodes surfaces, are investigated. The results show that rectifying performance and negative differential resistance (NDR) behaviors can be enhanced obviously by increasing the length. Analysis of Mülliken population, transmission spectra, evolutions of frontier orbitals and molecular projected self-consistent Hamiltonian of molecular orbital indicate that electronic transmission strength, charge transfer and distributions of molecular states change are the intrinsic origin of these rectifying performances and NDR behaviors.
    Keywords: ATK; Application; wide band gap semiconductors; boron-nitride; doping; negative differential resistance; NDR
    Area: molecular electronics; nanowires
    BibTeX:
    @article{Qiu2013,
      author = {Qiu, M. and Liew, K. M.},
      title = {Length dependence of carbon-doped BN nanowires: A-D Rectification and a route to potential molecular devices},
      journal = {Journal of Applied Physics},
      publisher = {AIP},
      year = {2013},
      volume = {113},
      number = {5},
      pages = {054305},
      doi = {http://dx.doi.org/10.1063/1.4790306}
    }
    
    Hari Mohan Rai, Neeraj K. Jaiswal, Pankaj Srivastava & Rajnish Kurchania Electronic and Transport Properties of Zigzag Boron Nitride Nanoribbons 2013 Journal of Computational and Theoretical Nanoscience
    Vol. 10(2), 368-375 
    DOI  
    Abstract: We have systematically investigated the electronic and transport properties of bare and hydrogenated zigzag boron nitride nanoribbons (ZBNNRs). We employed the spin unrestricted density functional theory (DFT) calculations within the local spin density approximation (LSDA) to reveal the semi-metallicity in bare ZBNNRs. Both-edges H-termination turns the ribbons semiconducting. Moreover, the band gap of both-edges H-terminated ZBNNRs is inversely proportional to the ribbon width. Interestingly, only boron edge H-passivated ZBNNRs leads to semi-metallic character whereas only nitrogen edge H-termination exhibits semiconducting behavior. The breaking of degeneracy for up spin and down spin electrons, as observed in bare and one edge H-terminated ZBNNRs points towards the possibility of spin polarized current. The transmission spectrum (TS) analysis also confirms the separation of spin up and down electrons making ZBNNR a suitable candidate for spin filter devices and other spintronics applications.
    Keywords: ATK; Application; boron nitride nanoribbons; spin; band structures; density of states; transmission spectra
    Area: graphene; spin
    BibTeX:
    @article{Rai2013,
      author = {Rai, Hari Mohan and Jaiswal, Neeraj K. and Srivastava, Pankaj and Kurchania, Rajnish},
      title = {Electronic and Transport Properties of Zigzag Boron Nitride Nanoribbons},
      journal = {Journal of Computational and Theoretical Nanoscience},
      year = {2013},
      volume = {10},
      number = {2},
      pages = {368--375},
      doi = {http://dx.doi.org/10.1166/jctn.2013.2706}
    }
    
    S Barzilai, F Tavazza & L E Levine The effect of internal impurities on the mechanical and conductance properties of gold nanowires during elongation 2013 Modelling and Simulation in Materials Science and Engineering
    Vol. 21(2), 025004- 
    DOI  
    Abstract: The conductance and mechanical properties of contaminated gold nanowires (NWs) were studied using first principle calculations. Nanowires containing internal impurities of H 2 O or O 2 were elongated along two different directions. It was found that both impurities interact with the gold atoms and affect the properties of the NWs. From a mechanical viewpoint, the impurities increase the bond strength in their vicinity and, throughout the entire elongation, remain surrounded by gold atoms. The impurities do not migrate to the surface and never end up in the single atom chain. The NW fracture always occurs at an Au-Au bond, far from the impurity. Therefore, the impurities do not affect the fracture strength but do decrease the strain at fracture. A variety of conductance effects were observed depending on the type and location of the impurity, and the O 2 has the most significant impact. The O 2 reduces the conductance when it is close to the gold atoms in the main pathway. However, at the late stages of the elongation, both impurities are located far from the main pathway and have little influence on the conductance.
    Keywords: ATK; ATK-SE; Application; nanowire; mechanical properties; deformation; plasticity; defects; structural failure; quantum wire; nanowire; atomic wire; nanowire;
    Area: nanowires
    BibTeX:
    @article{Barzilai2013,
      author = {Barzilai, S and Tavazza, F and Levine, L E},
      title = {The effect of internal impurities on the mechanical and conductance properties of gold nanowires during elongation},
      journal = {Modelling and Simulation in Materials Science and Engineering},
      year = {2013},
      volume = {21},
      number = {2},
      pages = {025004--},
      doi = {http://dx.doi.org/10.1088/0965-0393/21/2/025004}
    }
    
    Yukihito Matsuura Current rectification in nickelocenylferrocene sandwiched between two gold electrodes 2013 J. Chem. Phys.
    Vol. 138(1), 014311-4 
    DOI  
    Abstract: I present a theoretical study of the electronic transport properties of nickelocenylferrocene sandwiched between gold electrodes. Compared with the biferrocene system, the nickelocenylferrocene system had high electrical conduction and rectification in the bias range -1 to 1 V. Furthermore, the spin-down states of the nickelocenylferrocene system exhibited perfect spin-filtering properties. From the electronic states of the nickelocenylferrocene, it was found that the rectification was caused by a difference in the bias-dependent behaviors between the Fe 3d and Ni 3d orbitals.
    Keywords: electrical conductivity, nickel compounds, organic compounds, rectification, ATK, Application, spin
    Area: molecular electronics; spin
    BibTeX:
    @article{Matsuura2013,
      author = {Matsuura, Yukihito},
      title = {Current rectification in nickelocenylferrocene sandwiched between two gold electrodes},
      journal = {J. Chem. Phys.},
      publisher = {AIP},
      year = {2013},
      volume = {138},
      number = {1},
      pages = {014311--4},
      doi = {http://dx.doi.org/10.1063/1.4773404}
    }
    
    Haiqing Wan, Benhu Zhou, Wenhu Liao & Guanghui Zhou Spin-filtering and rectification effects in a Z-shaped boron nitride nanoribbon junction 2013 The Journal of Chemical Physics
    Vol. 138(3), 034705 
    DOI  
    Abstract: A Z-shaped junction constructed by a few-nanometer-long armchair-edged boron nitride nanoribbon (ABNNR) sandwiched between two semi-infinite zigzag-edged BNNR electrodes with different hydrogen-passivated edge treatment is proposed, and its spin-dependent electronic transport is studied by ab initio calculations. It is found that a short ABNNR exhibits metallic behavior and can be used as a conduction channel. Interestingly, the spin-filtering and rectification effects exist in the junctions without any edge passivation or with boron-edge passivation. The analysis on the projected density of states and spatial distribution of molecular projected self-consistent Hamiltonian eigenstates gives an insight into the observed results for the system. Our results suggest that a BNNR-based nanodevices with spin-filtering and rectification effects may be synthesized from an hexagonal boron nitride sheet by properly tailoring and edge passivation.
    Keywords: ATK; Application; ab initio calculations; boron compounds; electrodes; electronic density of states; III-V semiconductors; nanoribbons; passivation; rectification; SCF calculations; wide band gap semiconductors; molecular rectifiers; graphene; transport; edges
    Area: graphene
    BibTeX:
    @article{Wan2013,
      author = {Haiqing Wan and Benhu Zhou and Wenhu Liao and Guanghui Zhou},
      title = {Spin-filtering and rectification effects in a Z-shaped boron nitride nanoribbon junction},
      journal = {The Journal of Chemical Physics},
      publisher = {AIP},
      year = {2013},
      volume = {138},
      number = {3},
      pages = {034705},
      doi = {http://dx.doi.org/10.1063/1.4775841}
    }
    
    Neng-Ping Wang & Xiao-Jun Xu Effects of defects near source or drain contacts of carbon nanotube transistors 2012 EPL (Europhysics Letters)
    Vol. 100(4), 47009- 
    DOI URL 
    Abstract: We calculate the amplitude of the random-telegraph-signal (RTS) noise due to a single charged defect in a long-channel p-type carbon nanotube field-effect transistor, using the nonequilibrium Green function method in a tight-binding approximation. We find that the amplitude of the RTS noise caused by a positive charge close to the source (or drain) contact increases with the applied gate voltage and drain voltage. A positive charge located at the nanotube-oxide interface and close to the source (or drain) contact may cause a large RTS noise of about 50% in the on-state.
    Keywords: Application; ATK-SE; field-effect transistors; random-telegraph-signal; low-frequency noise; 1/f noise; fluctuations; interface
    Area: nanotubes
    BibTeX:
    @article{Wang2012c,
      author = {Wang, Neng-Ping and Xu, Xiao-Jun},
      title = {Effects of defects near source or drain contacts of carbon nanotube transistors},
      journal = {EPL (Europhysics Letters)},
      year = {2012},
      volume = {100},
      number = {4},
      pages = {47009--},
      url = {http://stacks.iop.org/0295-5075/100/i=4/a=47009},
      doi = {http://dx.doi.org/10.1209/0295-5075/100/47009}
    }
    
    Jiaxin Zheng, Chengyong Xu, Lu Wang, Qiye Zheng, Hong Li, Qihang Liu, Ruge Quhe, Zhengxiang Gao, Junjie Shi & Jing Lu Sign-changeable spin-filter efficiency in linear carbon atomic chain 2013 Physica E: Low-dimensional Systems and Nanostructures
    Vol. 48(0), 101-105 
    DOI URL 
    Abstract: It is well known that there is spin-filter efficiency (SFE) of a linear carbon atomic chain. In this article, we examine the quantum transport calculations of a linear carbon atomic chain connected to two half-planar graphene electrodes by using the first-principle method and reveal for the first time that sign of the SFE of such carbon atomic chain is changeable with the bias. This makes the carbon atomic chains attractive to potential application of spintronics.
    Keywords: ATK; Application; graphene; molecular electronics; atomic chain; spin filter;
    Area: molecular electronics; graphene; spin
    BibTeX:
    @article{Zheng2013,
      author = {Zheng, Jiaxin and Xu, Chengyong and Wang, Lu and Zheng, Qiye and Li, Hong and Liu, Qihang and Quhe, Ruge and Gao, Zhengxiang and Shi, Junjie and Lu, Jing},
      title = {Sign-changeable spin-filter efficiency in linear carbon atomic chain},
      journal = {Physica E: Low-dimensional Systems and Nanostructures},
      year = {2013},
      volume = {48},
      number = {0},
      pages = {101--105},
      url = {http://www.sciencedirect.com/science/article/pii/S1386947712004778},
      doi = {http://dx.doi.org/10.1016/j.physe.2012.12.009}
    }
    
    Satyendra Singh Chauhan, Pankaj Srivastava & A.K. Shrivastava Band gap engineering in doped graphene nanoribbons: An ab initio approach 2013 Solid State Communications
    Vol. 154(0), 69-71 
    DOI URL 
    Abstract: We present first principle study for stability and electronic properties of armchair graphene nanoribbons (AGNRs). We have investigated the stability and electronic properties of armchair graphene nanoribbons whose edges are doped with (i) s-type elements, Mg (ii) p-type elements, B and S, and (iii) 3d-type TMs, Ti and Mn, atoms using density functional theory. We predict that transition metals as substitutional dopant in AGNRs are energetically more favorable and minimize the band gap. The edges of the AGNRs are chemically more active and they can accommodate appropriate dopants to obtain different electronic properties having the same geometrical structure of the ribbon. Our results suggest that such materials can be used for nanoelectronic and spintronic applications.
    Keywords: ATK, Application, graphene nanoribbons, density functional theory, stability, band gap
    Area: graphene
    BibTeX:
    @article{Chauhan2013,
      author = {Chauhan, Satyendra Singh and Srivastava, Pankaj and Shrivastava, A.K.},
      title = {Band gap engineering in doped graphene nanoribbons: An ab initio approach},
      journal = {Solid State Communications},
      year = {2013},
      volume = {154},
      number = {0},
      pages = {69--71},
      url = {http://www.sciencedirect.com/science/article/pii/S0038109812005832},
      doi = {http://dx.doi.org/10.1016/j.ssc.2012.10.030}
    }
    
    Sudhanshu Choudhary & S. Qureshi Theoretical study on the effect of dopant positions and dopant density on transport properties of a BN co-doped SiC nanotube 2013 Physics Letters A
    Vol. 377(5), 430-435 
    DOI URL 
    Abstract: We investigate the effect of dopant (boron 'B' - nitrogen 'N') position and density on electronic transport properties of a BN co-doped silicon carbide nanotube (SiCNT). The results show an increase in conductance when both BN impurities are far in space from each other. Orbital delocalization and appearance of new electronic states around Fermi level contribute to the current when this spacing is increased. On the other hand, a reduction in SiCNT conductivity was observed when BN dopant density was increased. This is attributed to the electronic states moving away from the Fermi level and orbital localization at higher bias voltages.
    Keywords: ATK; Application; ab initio; DFT; NEGF; SiCNT; nanotubes; doping; silicon-carbide nanotubes; electron-transport
    Area: nanotubes
    BibTeX:
    @article{Choudhary2013,
      author = {Choudhary, Sudhanshu and Qureshi, S.},
      title = {Theoretical study on the effect of dopant positions and dopant density on transport properties of a BN co-doped SiC nanotube},
      journal = {Physics Letters A},
      year = {2013},
      volume = {377},
      number = {5},
      pages = {430--435},
      url = {http://www.sciencedirect.com/science/article/pii/S0375960112012753},
      doi = {http://dx.doi.org/10.1016/j.physleta.2012.12.007}
    }
    
    X.J. Tan, H.J. Liu, J. Wei, J. Shi, X.F. Tang & C. Uher Thermoelectric properties of small diameter carbon nanowires 2013 Carbon
    Vol. 53(0), 286-291 
    URL 
    Abstract: The room temperature thermoelectric properties of three kinds of small diameter carbon nanowires are investigated by using nonequilibrium Green's function method and molecular dynamics simulations. Due to very low thermal conductance and a relatively high power factor, these nanowires are found to exhibit better thermoelectric performance than other low-dimensional carbon-based materials such as carbon nanotubes. Moreover, the ZT values of these systems can be further increased to about 10 by partial passivation of hydrogen, which greatly reduces both the electron and phonon contributions to the thermal conductance, but leaves the power factor less affected.
    Keywords: ATK; Application; carbon nanowire; thermoelectric properties; ZT; passivation; thermal conductance; nonequilibrium molecular-dynamics; thermal conductivity; nanowires; simulation; nanotubes; figure; merit of performance; metals
    Area: nanowires; thermo
    BibTeX:
    @article{Tan2013,
      author = {Tan, X.J. and Liu, H.J. and Wei, J. and Shi, J. and Tang, X.F. and Uher, C.},
      title = {Thermoelectric properties of small diameter carbon nanowires},
      journal = {Carbon},
      year = {2013},
      volume = {53},
      number = {0},
      pages = {286--291},
      url = {http://www.sciencedirect.com/science/article/pii/S0008622312008731}
    }
    
    X.Z. Wu, J. Xiao, L.N. Chen, C. Cao, H. Xu & M.Q. Long The effect of asymmetrical electrode on the transport properties of molecular devices 2013 Physica B: Condensed Matter
    Vol. 411(0), 131-135 
    DOI URL 
    Abstract: By applying nonequilibrium Green's functions in combination with the density functional theory, we have investigated the electronic transport properties of molecular devices consisting of the carbon atomic chain coupling with symmetry and asymmetry Au electrodes. The asymmetry Au electrodes systems display good rectifying behavior. The main origin of this phenomenon is that a molecular core coupling with asymmetry electrodes can generate two asymmetrical Schottky barriers at both extended molecule regions. This rectification is also explained by the calculated transmission spectrum and the spatial distribution of the LUMO and HOMO states.
    Keywords: Transport properties, Molecular device, Rectifying behavior, Asymmetry electrode, atomic chain, ATK, Application
    Area: molecular electronics
    BibTeX:
    @article{Wu2013,
      author = {Wu, X.Z. and Xiao, J. and Chen, L.N. and Cao, C. and Xu, H. and Long, M.Q.},
      title = {The effect of asymmetrical electrode on the transport properties of molecular devices},
      journal = {Physica B: Condensed Matter},
      year = {2013},
      volume = {411},
      number = {0},
      pages = {131--135},
      url = {http://www.sciencedirect.com/science/article/pii/S0921452612010241},
      doi = {http://dx.doi.org/10.1016/j.physb.2012.11.028}
    }
    
    Penchalaiah Palla & J.P. Raina Effect of Hexagonal Boron Nitride on Energy Band Gap of Graphene Antidot Structures 2012 Innovative Systems Design and Engineering
    Vol. 3(12), 27-39 
    URL 
    Abstract: The zero band gap (Eg) graphene becomes narrow Eg semiconductor when graphene is patterned with periodic array of hexagonal shaped antidots, the resultant is the hexagonal Graphene Antidot Lattice (hGAL). Based on the number of atomic chains between antidots, hGALs can be even and odd. The even hGALs (ehGAL) are narrow Eg semiconductors and odd hGALs (ohGAL) are semi-metals. The Eg opening up by hGALs is not sufficient to operate a realistic switching transistor. Also hGAL transistors realized on Si/SiO2 substrate are suffering with low carrier mobility and ON-OFF current ratio. In order to achieve a sizable Eg with good mobility, AB Bernal stacked hGALs on hexagonal Boron Nitride (hBN), ABA Bernal stacked hBN / hGAL / hBN sandwiched structures and AB misaligned hGAL /hBN structures are reported here for the first time. Using the first principles method the electronic structure calculations are performed. A sizable Eg of about 1.04 eV (940+100 meV ) is opened when smallest neck width medium radius ehGAL supported on hBN and about 1.1 eV (940 + 200 meV ) is opened when the same is sandwiched between hBN layers. A band gap on the order of 71 meV is opened for Bernal stacked ohGAL / hBN and nearly 142 meV opened for hBN / ohGAL /hBN structures for smallest radius and width of nine atomic chains between antidots. Unlike a misaligned graphene on hBN, the misaligned ohGAL/hBN structure shows increased Eg. This study could open up new ways of band gap engineering for graphene based nanostructures.
    Keywords: ATK-SE, ATK, Application, Graphene, graphene antidots, hexagonal boron nitride, band structure, band gap engineering
    Area: graphene
    BibTeX:
    @article{Palla2012,
      author = {Penchalaiah Palla and J.P. Raina},
      title = {Effect of Hexagonal Boron Nitride on Energy Band Gap of Graphene Antidot Structures},
      journal = {Innovative Systems Design and Engineering},
      year = {2012},
      volume = {3},
      number = {12},
      pages = {27-39},
      url = {http://www.iiste.org/Journals/index.php/ISDE/article/view/3653}
    }
    
    Zhi-Qiang Fan, Zhen-Hua Zhang, Xiao-Qing Deng, Gui-Ping Tang & Ke-Qiu Chen Reversible switching in an N-salicylideneaniline molecular device induced by hydrogen transfer 2012 Organic Electronics
    Vol. 13(12), 2954-2958 
    DOI  
    Abstract: By applying nonequilibrium Green's functions in combination with the density-functional theory, we investigate the electronic transport properties of an N-salicylideneaniline molecule sandwiched between two Au electrodes. The results show that the currents between the enol and keto tautomeric forms of the molecule vary widely and a reversible switching behavior can be found in this device due to the photoinduced hydrogen transfer. In addition, the current switching ratio which is a typical character of switching behavior will lower a little when an electron-donating group (-NH2) substitutes the right end hydrogen atom of the N-salicylideneaniline molecule. However, the substituent of an electron-withdrawing group (-NO2) on the same site can enlarge the current switching ratio two orders of magnitude, which greatly improve the potential of the N-salicylideneaniline molecular device in future logic and memory.
    Keywords: Molecular device, Electronic transport, Switching behavior, ATK, Application
    Area: molecular electronics
    BibTeX:
    @article{Fan2012c,
      author = {Fan, Zhi-Qiang and Zhang, Zhen-Hua and Deng, Xiao-Qing and Tang, Gui-Ping and Chen, Ke-Qiu},
      title = {Reversible switching in an N-salicylideneaniline molecular device induced by hydrogen transfer},
      journal = {Organic Electronics},
      year = {2012},
      volume = {13},
      number = {12},
      pages = {2954--2958},
      doi = {http://dx.doi.org/10.1016/j.orgel.2012.08.019}
    }
    
    Mausumi Chattopadhyaya, Md. Mehboob Alam, Sabyasachi Sen & Swapan Chakrabarti Electrostatic Spin Crossover and Concomitant Electrically Operated Spin Switch Action in a Ti-Based Endohedral Metallofullerene Polymer 2012 Physical Review Letters
    Vol. 109(25), 257204- 
    DOI  
    Abstract: Herein, we predict that a 1D chain of Ti@C32-C2-Ti@C32 (TEMF) will act as a spin switch in the presence of an electric field. The spin resolved density of states analyses reveal that, surprisingly, both the low- and high-spin states of TEMF are half-metal; however, the metallic density of states comes from the opposite spin channels of the two spin states. More remarkably, it is found that the electric field driven spin crossover between the low and high state in TEMF is achievable at field strength 1.04 V/nm, which eventually leads to the realization of the first ever electrically operated spin switch device.
    Keywords: ATK; Application; molecular electronics; atomic chain; spin switch; fullerenes
    Area: molecular electronics; fullerenes; spin
    BibTeX:
    @article{Chattopadhyaya2012,
      author = {Chattopadhyaya, Mausumi and Alam, Md. Mehboob and Sen, Sabyasachi and Chakrabarti, Swapan},
      title = {Electrostatic Spin Crossover and Concomitant Electrically Operated Spin Switch Action in a Ti-Based Endohedral Metallofullerene Polymer},
      journal = {Physical Review Letters},
      publisher = {American Physical Society},
      year = {2012},
      volume = {109},
      number = {25},
      pages = {257204--},
      doi = {http://dx.doi.org/10.1103/PhysRevLett.109.257204}
    }
    
    R.K. Ghosh, S. Bhattacharya & S. Mahapatra Physics-Based Band Gap Model for Relaxed and Strained [100] Silicon Nanowires 2012 Electron Devices, IEEE Transactions on
    Vol. 59(6)Electron Devices, IEEE Transactions on, 1765-1772 
    DOI  
    Abstract: In this paper, we propose a physics-based simplified analytical model of the energy band gap and electron effective mass in a relaxed and strained rectangular [100] silicon nanowires (SiNWs). Our proposed formulation is based on the effective mass approximation for the nondegenerate two-band model and 4 x 4 Lüttinger Hamiltonian for energy dispersion relation of conduction band electrons and the valence band heavy and light holes, respectively. Using this, we demonstrate the effect of the uniaxial strain applied along [100]-direction and a biaxial strain, which is assumed to be decomposed from a hydrostatic deformation along [001] followed by a uniaxial one along the [100]-direction, respectively, on both the band gap and the transport and subband electron effective masses in SiNW. Our analytical model is in good agreement with the extracted data using the extended-Hückel-method-based numerical simulations over a wide range of device dimensions and applied strain.
    Keywords: ATK-SE, Application, Analytical models, Dispersion, Effective mass, Photonic band gap, Silicon, Strain, Wires, deformation, electrons, elemental semiconductors, hydrostatics, nanowires, numerical analysis, silicon, Lüttinger Hamiltonian, Si, biaxial strain, conduction band electron, effective mass approximation, electron effective mass, energy band gap, energy dispersion relation, extended-Hückel-method-based numerical simulation, hydrostatic deformation, nondegenerate two-band model, physics-based band gap model, physics-based simplified analytical model, relaxed nanowire, strained nanowire, uniaxial strain effect, valence band heavy hole, valence band light hole, Band gap, effective mass, nanowires, size quantization, strain
    Area: semi
    BibTeX:
    @article{Ghosh2012,
      author = {Ghosh, R.K. and Bhattacharya, S. and Mahapatra, S.},
      title = {Physics-Based Band Gap Model for Relaxed and Strained [100] Silicon Nanowires},
      booktitle = {Electron Devices, IEEE Transactions on},
      journal = {Electron Devices, IEEE Transactions on},
      year = {2012},
      volume = {59},
      number = {6},
      pages = {1765--1772},
      doi = {http://dx.doi.org/10.1109/TED.2012.2190737}
    }
    
    Ram Krishna Ghosh, Sitangshu Bhattacharya & Santanu Mahapatra k.p based closed form energy band gap and transport electron effective mass model for [100] and [110] relaxed and strained Silicon nanowire 2013 Solid-State Electronics
    Vol. 80(0), 124-134 
    DOI URL 
    Abstract: In this paper, we address a physics based closed form model for the energy band gap (Eg) and the transport electron effective mass in relaxed and strained [1 0 0] and [1 1 0] oriented rectangular Silicon Nanowire (SiNW). Our proposed analytical model along [1 0 0] and [1 1 0] directions are based on the k.p formalism of the conduction band energy dispersion relation through an appropriate rotation of the Hamiltonian of the electrons in the bulk crystal along [0 0 1] direction followed by the inclusion of a 4 x Lüttinger Hamiltonian for the description of the valance band structure. Using this, we demonstrate the variation in Eg and the transport electron effective mass as function of the cross-sectional dimensions in a relaxed [1 0 0] and [1 1 0] oriented SiNW. The behaviour of these two parameters in [1 0 0] oriented SiNW has further been studied with the inclusion of a uniaxial strain along the transport direction and a biaxial strain, which is assumed to be decomposed from a hydrostatic deformation along [0 0 1] with the former one. In addition, the energy band gap and the effective mass of a strained [1 1 0] oriented SiNW has also been formulated. Using this, we compare our analytical model with that of the extracted data using the nearest neighbour empirical tight binding sp3d5s* method based simulations and has been found to agree well over a wide range of device dimensions and applied strain.
    Keywords: Silicon nanowire, Size quantization, Band gap, Effective mass, Strain, ATK-SE, Application
    Area: semi
    BibTeX:
    @article{Ghosh2013a,
      author = {Ghosh, Ram Krishna and Bhattacharya, Sitangshu and Mahapatra, Santanu},
      title = {k.p based closed form energy band gap and transport electron effective mass model for [100] and [110] relaxed and strained Silicon nanowire},
      journal = {Solid-State Electronics},
      year = {2013},
      volume = {80},
      number = {0},
      pages = {124--134},
      url = {http://www.sciencedirect.com/science/article/pii/S0038110112003516},
      doi = {http://dx.doi.org/10.1016/j.sse.2012.11.001}
    }
    
    Y. Al & H.L. Zhang Construction and Conductance Measurement of Single Molecule Junctions 2012 Acta Physico-chimica Sinica
    Vol. 28(10), 2237-2248 
    DOI  
    Abstract: Molecular electronics has become an important research field in the past decade, and molecular devices can be used as molecular wires, switches, rectifiers, and transistors etc. Construction of metal/molecule/metal (MMM) junctions is the most effective method for investigating the charge transport properties of molecular devices. However, the measurement of individual molecule junctions at the nanoscale is still very challenging because of many technical difficulties. This paper reviews the recent progress and the challenges in the measurement of single molecule conductance, and summarizes investigation of the charge transport mechanism.
    Keywords: atomic-force microscopy; walled carbon nanotubes; electronic devices; charge-transport; electrical conductance; quantum transport; metal nanowires; break junctions; scanning probe; spin; ATK; Application
    Area: molecular electronics
    BibTeX:
    @article{Al2012,
      author = {Al, Y. and Zhang, H. L.},
      title = {Construction and Conductance Measurement of Single Molecule Junctions},
      journal = {Acta Physico-chimica Sinica},
      publisher = {Peking Univ Press},
      year = {2012},
      volume = {28},
      number = {10},
      pages = {2237--2248},
      doi = {http://dx.doi.org/10.3866/PKU.WHXB201209102}
    }
    
    Sudhanshu Choudhary & S. Qureshi Effect of moisture on electron transport in SiC nanotubes: An ab-initio study 2012 Physics Letters A
    Vol. 376(45), 3359-3362 
    DOI URL 
    Abstract: We investigate the effect of moisture-adsorption on the electronic transport properties of a silicon-carbide nanotube (SiCNT). The results obtained by relaxing an H2O (water) molecule over an (8,0 ) SiCNT show that water molecule binds with SiCNT. The formation of SiO bond (bond length 1.95 Å) between the SiCNT and H2O molecule was discovered. However, previous studies on H2O adsorbtion in carbon nanotubes (CNTs) have shown the formation of CH bond at the CNT surface. Current-voltage (I-V) characteristics show a reduction in SiCNT conductivity when the number of H2O molecules over SiCNT were increased.
    Keywords: ATK; Application; sensor; ab-initio; DFT; NEGF; SiCNT; carbon nanotube;
    Area: nanotubes
    BibTeX:
    @article{Choudhary2012a,
      author = {Choudhary, Sudhanshu and Qureshi, S.},
      title = {Effect of moisture on electron transport in SiC nanotubes: An ab-initio study},
      journal = {Physics Letters A},
      year = {2012},
      volume = {376},
      number = {45},
      pages = {3359--3362},
      url = {http://www.sciencedirect.com/science/article/pii/S0375960112009693},
      doi = {http://dx.doi.org/10.1016/j.physleta.2012.08.052}
    }
    
    R.K. Ghosh & S. Mahapatra Direct Band-to-Band Tunneling in Reverse Biased MoS2 Nanoribbon p-n Junctions 2013 IEEE Transactions on Electron Devices
    Vol. 60(1), 274-279 
    DOI  
    Abstract: We investigate the direct band-to-band tunneling (BTBT) in a reverse biased molybdenum disulfide (MoS2) nanoribbon p-n junction by analyzing the complex band structure obtained from semiempirical extended Hückel method under relaxed and strained conditions. It is demonstrated that the direct BTBT is improbable in relaxed monolayer nanoribbon; however, with the application of certain uniaxial tensile strain, the material becomes favorable for it. On the other hand, the relaxed bilayer nanoribbon is suitable for direct BTBT but becomes unfavorable when the applied uniaxial tensile or compressive strain goes beyond a certain limit. Considering the Wentzel-Kramers-Brillouin approximation, we evaluate the tunneling probability to estimate the tunneling current for a small applied reverse bias. Reasonably high tunneling current in the MoS2 nanoribbons shows that it can take advantage over graphene nanoribbon in future tunnel field-effect transistor applications.
    Keywords: ATK-SE, Application, bandgap, band-to-band tunneling (BTBT), complex band structure, nanoribbon, strain, MoS2
    Area: graphene; dichalcogenides
    BibTeX:
    @article{Ghosh2013,
      author = {Ghosh, R. K. and Mahapatra, S.},
      title = {Direct Band-to-Band Tunneling in Reverse Biased MoS2 Nanoribbon p-n Junctions},
      journal = {IEEE Transactions on Electron Devices},
      year = {2013},
      volume = {60},
      number = {1},
      pages = {274-279},
      doi = {http://dx.doi.org/10.1109/TED.2012.2226729}
    }
    
    Yan-Dong Guo, Xiao-Hong Yan & Yang Xiao Computational Investigation of DNA Detection Using Single-Electron Transistor-Based Nanopore 2012 J. Phys. Chem. C
    Vol. 116(40)The Journal of Physical Chemistry C, 21609-21614 
    DOI  
    Abstract: We propose a single-electron transistor (SET)-based nanopore sensor for DNA sequencing, which consists of source, drain, and gate electrodes, as well as a nanopore where the DNA molecule is pulled through. For nanopore sensors based on transverse electronic transport, generally, the tunneling current is relatively small due to the weak coupling between the molecule and electrodes. We take full advantage of this feature by introducing SET to make the device operate in Coulomb-blockade regime. Through first-principles simulations, the charge stability diagrams of the nucleobases within the SET-nanopore environment are demonstrated to be distinctive for each molecule and, more importantly, independent of the nucleobase orientation, which can be served as electronic fingerprint for detection. We show that identifying the nucleobases can be achieved only though several specific regions or points in the diagram.
    Keywords: ATK; Application; single-electron transistor; set; sensor; dna sequencing; nucleoside; graphene nanopores; nucleotides; translocation; molecules; transport; capacitor; energies; device; holes; edge
    Area: molecular electronics; SET;
    BibTeX:
    @article{Guo2012a,
      author = {Guo, Yan-Dong and Yan, Xiao-Hong and Xiao, Yang},
      title = {Computational Investigation of DNA Detection Using Single-Electron Transistor-Based Nanopore},
      booktitle = {The Journal of Physical Chemistry C},
      journal = {J. Phys. Chem. C},
      publisher = {American Chemical Society},
      year = {2012},
      volume = {116},
      number = {40},
      pages = {21609--21614},
      doi = {http://dx.doi.org/10.1021/jp305909p}
    }
    
    Jun He & Ke-Qiu Chen Rectifying and perfect spin filtering behavior realized by tailoring graphene nanoribbons 2012 J. Appl. Phys.
    Vol. 112(11), 114319-5 
    DOI  
    Abstract: An armchair graphene nanoribbon based electronic device with spin filtering and rectifying behavior is designed by means of molecular tailoring, and the electronic transport properties are calculated by using nonequilibrium Green's functions in combination with the density functional theory. The results show that the rectifying behavior can be observed in the junctions, and the rectifying ratio can be effectively tuned by edge doping. Furthermore, perfect spin polarization behavior can also be observed in the junctions.
    Keywords: ATK, Application, density functional theory, fullerene devices, graphene, green's function methods, nanoelectronics, nanoribbons, rectification, spin polarised transport, field-effect transistors, transport-properties, room-temperature, heterojunctions
    Area: graphene; spin
    BibTeX:
    @article{He2012b,
      author = {He, Jun and Chen, Ke-Qiu},
      title = {Rectifying and perfect spin filtering behavior realized by tailoring graphene nanoribbons},
      journal = {J. Appl. Phys.},
      publisher = {AIP},
      year = {2012},
      volume = {112},
      number = {11},
      pages = {114319--5},
      doi = {http://dx.doi.org/10.1063/1.4768727}
    }
    
    Golam Rasul Ahmed Jamal & Md Shamsul Arefin Empirical Equation of Tight Binding Model Parameter to Calculate Bandgap of Semiconducting Single Wall Carbon Nanotube 2012 Journal of Electrical Engineering, The Institution of Engineers, Bangladesh
    Vol. 37(2), 3 
    URL 
    Abstract: Both Mod 1 and Mod 2 type semiconducting single wall carbon nanotubes over a wide diameter range are studied separately to find their band gap trend. For accurate calculation of their band gaps, modification of nearest-neighbor hopping parameter of the tight-binding model is proposed by considering it as a function of nanotube chiral index and mod value. A simple empirical equation for the nearest-neighbor hopping parameter is presented to produce band gaps of these nanotubes that agree well with simulated data. Empirical data are also compared with experimental data and found to be in excellent agreement with it after adding a flat correction.
    Keywords: ATK-SE; Application; tight-binding; carbon nanotube; band gap; nearest neighbor hopping parameter; tight-binding model; chiral index
    Area: nanotubes
    BibTeX:
    @article{Jamal2012,
      author = {Golam Rasul Ahmed Jamal and Md Shamsul Arefin},
      title = {Empirical Equation of Tight Binding Model Parameter to Calculate Bandgap of Semiconducting Single Wall Carbon Nanotube},
      journal = {Journal of Electrical Engineering, The Institution of Engineers, Bangladesh},
      year = {2012},
      volume = {37},
      number = {2},
      pages = {3},
      url = {http://www.banglajol.info/bd/index.php/JEE/article/view/12671}
    }
    
    Ahmed Mahmoud & Paolo Lugli Designing the rectification behavior of molecular diodes 2012 J. Appl. Phys.
    Vol. 112(11), 113720-5 
    DOI  
    Abstract: Thanks to major advances in chemical and fabrication processes, various electronic devices based on single molecules have been demonstrated. On the theoretical level, many attempts have been made to provide a clear view of the charge transport mechanism through molecules. However, the overall picture is not yet complete. In this study, we show that the rectification of a molecular device can be controlled by enforcing the potential drop profile along the molecule. The insertion of a resistive molecular path near the metallic electrode(s) can drastically alter the rectification behavior. Our observation paves the way for a better control of molecular devices.
    Keywords: ATK-SE; Application; diodes; molecular electronics; transport; nanostructures; protonation; inversion; device
    Area: molecular electronics
    BibTeX:
    @article{Mahmoud2012a,
      author = {Mahmoud, Ahmed and Lugli, Paolo},
      title = {Designing the rectification behavior of molecular diodes},
      journal = {J. Appl. Phys.},
      publisher = {AIP},
      year = {2012},
      volume = {112},
      number = {11},
      pages = {113720--5},
      doi = {http://dx.doi.org/10.1063/1.4768924}
    }
    
    Yukihito Matsuura Electron Transport in Polymeric µ-Cyclopentadienylelement Complexes of the Main Group Elements 2012 Molecular Crystals and Liquid Crystals
    Vol. 569(1)Molecular Crystals and Liquid Crystals, 103-111 
    DOI  
    Abstract: I examined electrical conduction in polymeric µ-cyclopentadienylelement (Cp-E) complexes of the main group elements using the nonequilibrium Green's function formalism with the density functional theory. The polymeric Cp-E complexes of group 1 elements, which had ionic Cp-E bonds, showed very low conductance. In contrast, the polymeric Cp-E complexes of groups 13 and 14 elements exhibited enhanced n-type electrical conduction when a bias was applied between the electrodes, because the delocalized electronic states of the lowest unoccupied molecular orbital were within the bias window.
    Keywords: ATK; Application; molecular electronics; cyclopentadienyl complex; DFT; electron transport; NEGF
    Area: molecular electronics
    BibTeX:
    @article{Matsuura2012a,
      author = {Matsuura, Yukihito},
      title = {Electron Transport in Polymeric µ-Cyclopentadienylelement Complexes of the Main Group Elements},
      booktitle = {Molecular Crystals and Liquid Crystals},
      journal = {Molecular Crystals and Liquid Crystals},
      publisher = {Taylor & Francis},
      year = {2012},
      volume = {569},
      number = {1},
      pages = {103--111},
      doi = {http://dx.doi.org/10.1080/15421406.2012.689575}
    }
    
    Fanben Meng, Yves-Marie Hervault, Lucie Norel, Karine Costuas, Colin Van Dyck, Victor Geskin, Jerome Cornil, Huey Hoon Hng, Stephane Rigaut & Xiaodong Chen Photo-modulable molecular transport junctions based on organometallic molecular wires 2012 Chem. Sci.
    Vol. 3(10), 3113-3118 
    DOI  
    Abstract: Photo-modulable molecular transport junctions are developed via on-wire lithography-fabricated nanogaps functionalized with a dithienylethene unit bearing two ruthenium fragments. A reversible and repeatable bi-state conductive switching upon alternate irradiation of UV and visible light can be distinctly observed. Theoretical calculations further suggest that bi-directional isomerization is due to the ruthenium moieties that modulate judiciously the electronic coupling between the photochromic part and the metal electrodes, and that the differences in electronic structure between the two isomers (open and closed states) are responsible for conductivity switching.
    Keywords: ATK; Application; scanning-tunneling-microscopy; different oxidation-states; carbon-rich bridges; theoretical investigations; conductance; electronics; complexes; devices; ruthenium; temperature
    Area: molecular electronics
    BibTeX:
    @article{Meng2012,
      author = {Meng, Fanben and Hervault, Yves-Marie and Norel, Lucie and Costuas, Karine and Van Dyck, Colin and Geskin, Victor and Cornil, Jerome and Hng, Huey Hoon and Rigaut, Stephane and Chen, Xiaodong},
      title = {Photo-modulable molecular transport junctions based on organometallic molecular wires},
      journal = {Chem. Sci.},
      publisher = {The Royal Society of Chemistry},
      year = {2012},
      volume = {3},
      number = {10},
      pages = {3113--3118},
      doi = {http://dx.doi.org/10.1039/C2SC20323E}
    }
    
    Huaping Xiao, Yuanping Chen, Yuee Xie, Tao Ouyang, Ye Zhang & Jianxin Zhong The modification of central B/N atom chain on electron transport of graphene nanoribbons 2012 J. Appl. Phys.
    Vol. 112(11), 113713-5 
    DOI  
    Abstract: The electronic transport properties of hybrid graphene nanoribbons constructed by substituting C atom chain into B (N) atom chain are investigated through using the density functional theory in combination with the nonequilibrium Green's function method. It is found that the hybrid nanoribbon with armchair edge transits from semiconducting to metallic. While the transport properties of hybrid B (N) system with zigzag edge are highly improved with the transmission conductance around the Fermi level increasing to 6G0 (5G0). All these unique transport properties are mainly attributed to the coupling effect between B (N) atoms and C atoms at the interface of hybrid systems, which introduces a pair of bonding and antibonding bands around the Fermi level. The results indicate that such hybrid system is an effective way to modulate the transport properties of graphene nanoribbons.
    Keywords: density functional theory, electrical conductivity transitions, Fermi level, graphene, Green's function methods, metal-insulator transition, nanoribbons, phase, ATK, Application
    Area: graphene
    BibTeX:
    @article{Xiao2012a,
      author = {Xiao, Huaping and Chen, Yuanping and Xie, Yuee and Ouyang, Tao and Zhang, Ye and Zhong, Jianxin},
      title = {The modification of central B/N atom chain on electron transport of graphene nanoribbons},
      journal = {J. Appl. Phys.},
      publisher = {AIP},
      year = {2012},
      volume = {112},
      number = {11},
      pages = {113713--5},
      doi = {http://dx.doi.org/10.1063/1.4768719}
    }
    
    Yuqing Xu, Bin Cui, Guomin Ji, Dongmei Li & Desheng Liu Effect of the orientation of nitro group on the electronic transport properties in single molecular field-effect transistors 2013 Phys. Chem. Chem. Phys.
    Vol. 15(3), 832-836 
    DOI  
    Abstract: Molecular devices with nitro groups display unique electronic transport properties in experiments. By applying the non-equilibrium Green's function combined with density functional theory, we find that the orientation of the nitro group with respect to the backbone of the molecule has a crucial effect on the device performance and can show unusual experimental phenomena. Furthermore, molecular devices with a nitro group are sensitive to gate voltage and suitable for making effective single molecular field-effect transistors. These results provide an important theoretical support to experiments and the design of future molecular devices by using nitro groups.
    Keywords: ATK; Application; molecular electronics; single molecular field-effect transistor; switch; quantum transport
    Area: molecular electronics
    BibTeX:
    @article{Xu2013,
      author = {Xu, Yuqing and Cui, Bin and Ji, Guomin and Li, Dongmei and Liu, Desheng},
      title = {Effect of the orientation of nitro group on the electronic transport properties in single molecular field-effect transistors},
      journal = {Phys. Chem. Chem. Phys.},
      publisher = {The Royal Society of Chemistry},
      year = {2013},
      volume = {15},
      number = {3},
      pages = {832--836},
      doi = {http://dx.doi.org/10.1039/C2CP41480E}
    }
    
    Wei Yao, K.L. Yao, G.Y. Gao, S.C. Zhu & H.H. Fu Anisotropic transport properties of zinc-blend ZnTe/CrTe heterogeneous junction nanodevices 2012 J. Appl. Phys.
    Vol. 112(10), 103717-6 
    DOI  
    Abstract: Motivated by the molecular-beam epitaxial growth of zinc-blend-type CrTe thin films on ZnTe, we present a theoretical study on the spin-polarized transport properties of ZnTe/CrTe p-n junction as spin diode and CrTe/ZnTe/CrTe magnetic tunnel junction for (001) and (011) surfaces. Both ZnTe(001)/CrTe(001) and ZnTe(011)/CrTe(011) p-n junctions show excellent spin diode effect, the majority spin current of positive voltage is much larger than that of negative voltage and the minority spin current is absolutely inhibited. The ZnTe(001)/CrTe(001) p-n junction has lower "turn off" current and higher rectification ratio (about 10^5) than the ZnTe(011)/CrTe(011) which shows obvious anisotropy. We also find that the tunneling magneto resistance ratio of the CrTe/ZnTe/CrTe magnetic tunnel junction is up to about 4x10^9%.
    Keywords: ATK, , Application, chromium compounds, diodes, electron spin polarisation, molecular beam epitaxial growth, nanotechnology, p-n junctions, thin films, tunnelling magnetoresistance, wide band gap semiconductors, zinc compounds, MTJ, half-metallic ferromagnets, molecular-beam epitaxy, room-temperature, spintronics, magnetoresistance, semiconductors
    Area: interfaces; nvm; semi; spin
    BibTeX:
    @article{Yao2012,
      author = {Yao, Wei and Yao, K. L. and Gao, G. Y. and Zhu, S. C. and Fu, H. H.},
      title = {Anisotropic transport properties of zinc-blend ZnTe/CrTe heterogeneous junction nanodevices},
      journal = {J. Appl. Phys.},
      publisher = {AIP},
      year = {2012},
      volume = {112},
      number = {10},
      pages = {103717--6},
      doi = {http://dx.doi.org/10.1063/1.4767935}
    }
    
    J. Yu, G.L. Zhang, Y. Shang, K.D. Wang, H. Zhang, M. Sun, B. Liu & T. Zeng Transport properties of CNT/oligosilane/CNT heterojunctions 2013 Physica B: Condensed Matter
    Vol. 410(0), 237-243 
    DOI  
    Abstract: Combining the non-equilibrium Green's function formalism with density functional theory, the transport properties of nine CNT/oligosilane/CNT heterojunctions were systematically studied. We have found that the incorporation of oligosilane linkage to the carbon nanotube mouth could significantly tune the transport properties compared with the pure oligosilane and pure CNT. The P- and B-dopings upon the oligosilane moiety could not only enhance the conductivity but also give rise to multiple negative differential resistance behavior for the CNT/oligosilane/CNT heterojunctions. The concentration of heteroatom plays an important role in the transport properties of the CNT/oligosilane/CNT heterojunctions, while the number of the oligosilane linkage exerts little effect on the conductivity. The B-doped CNT/oligosilane/CNT heterojunctions show higher conductivity than those of the P-doped ones. The p-n junction caused by B- and P-codopings exhibits a rectifying effect and the rectification ratio is up to 7.19.
    Keywords: ATK; Application; theoretical study; transport property; carbon nanotube; oligosilane; doping; negative differential resistance; walled carbon nanotubes; silicon nanowire; peptide linkages; ab-initio; conductance; transistors; electrodes; molecules; diode
    Area: nanotubes
    BibTeX:
    @article{Yu2013,
      author = {Yu, J. and Zhang, G.L. and Shang, Y. and Wang, K.D. and Zhang, H. and Sun, M. and Liu, B. and Zeng, T.},
      title = {Transport properties of CNT/oligosilane/CNT heterojunctions},
      journal = {Physica B: Condensed Matter},
      year = {2013},
      volume = {410},
      number = {0},
      pages = {237--243},
      doi = {http://dx.doi.org/10.1016/j.physb.2012.11.016}
    }
    
    C.X. Zhang, Huaping Xiao, Chaoyu He, L. Xue, K.W. Zhang, L.Z. Sun & Jianxin Zhong Effects of contact oxidization on the transport properties of Au/ZGNR junctions 2012 Phys. Status Solidi RRL
    Vol. 6(12), 457-459 
    DOI  
    Abstract: The transport properties of the junction assembled by zigzag graphene nanoribbons (ZGNRs) and Au electrode (Au/ZGNR) are investigated using first-principles calculations. It is found that the Au/ZGNR junction behaves as a typical diode with Schottky barrier at the contact. Our results indicate that although the oxidization at the contact slightly influences the Schottky barrier, the I-V characteristic is effectively modulated. Such effect derives from the impact of the oxidization on the coupling between the ZGNRs and Au electrode.
    Keywords: ATK, Application, graphene nanoribbons, electronic transport, contact oxidization, gold electrodes, augmented-wave method, graphene nanoribbons, carbon nanotubes, electronics, oxide
    Area: graphene
    BibTeX:
    @article{Zhang2012g,
      author = {Zhang, C. X. and Xiao, Huaping and He, Chaoyu and Xue, L. and Zhang, K. W. and Sun, L. Z. and Zhong, Jianxin},
      title = {Effects of contact oxidization on the transport properties of Au/ZGNR junctions},
      journal = {Phys. Status Solidi RRL},
      publisher = {WILEY-VCH Verlag},
      year = {2012},
      volume = {6},
      number = {12},
      pages = {457--459},
      doi = {http://dx.doi.org/10.1002/pssr.201206409}
    }
    
    Yi-Peng An, Xinyuan Wei & Zhong-Qin Yang Improving electronic transport of zigzag graphene nanoribbons by ordered doping of B or N atoms 2012 Phys. Chem. Chem. Phys.
    Vol. 14(45), 15802-15806 
    DOI  
    Abstract: Using an ab initio method, we explored electronic structures and transport properties of zigzag graphene nanoribbons (ZGNRs) with ordered doping of B or N atoms. We find B or N atoms doping can increase significantly the conductance of the ZGNRs with an even number of zigzag chains due to additional conducting channels being induced and the breakdown of parity limitation. The higher the doping concentration, the larger the current amplification factor obtained. For the nanojunctions with one row B (or N) atoms, the current amplification factor can be larger when the doping position is near to the center, while for the junction with two rows, the trend is subtle due to the interactions between the two rows of B (or N) atoms. Negative differential resistive phenomena are found for the case of B doping at low concentrations and the case for N doping. The conductance of the ZGNR with odd numbers of zigzag chains can also be increased by doping of B or N atoms. More interestingly, the B or N doping can almost completely remove the even-odd effect on electronic transport of the ZGNRs. Our studies provide avenues to drastically improve the electronic transport of ZGNRs, helpful for graphene applications.
    Keywords: ATK; Application; doping; negative differential resistance; NDR; field-effect transistors
    Area: graphene
    BibTeX:
    @article{An2012c,
      author = {An, Yi-Peng and Wei, Xinyuan and Yang, Zhong-Qin},
      title = {Improving electronic transport of zigzag graphene nanoribbons by ordered doping of B or N atoms},
      journal = {Phys. Chem. Chem. Phys.},
      publisher = {The Royal Society of Chemistry},
      year = {2012},
      volume = {14},
      number = {45},
      pages = {15802--15806},
      doi = {http://dx.doi.org/10.1039/C2CP42123B}
    }
    
    L.N. Chen, C. Cao, X.Z. Wu, S.S. Ma, W.R. Huang & H. Xu Effects of partial hydrogenation on electronic transport properties in C60 molecular devices 2012 Solid State Communications
    Vol. 152(23), 2123-2127 
    DOI URL 
    Abstract: By using nonequilibrium Green's functions in combination with the density–function theory, we investigate electronic transport properties of molecular devices with pristine and partial hydrogenation. The calculated results show that the electronic transport properties of molecular devices can be modulated by partial hydrogenation. Interestingly, our results exhibit negative differential resistance behavior in the case of the imbalance H-adsorption in C60 molecular devices under low bias. However, negative differential resistance behavior cannot be observed in the case of the balance H-adsorption. A mechanism is proposed for the hydrogenation and negative differential resistance behavior.
    Keywords: ATK; Application; molecular device; transport property; hydrogenation; first-principles; fullerenes
    Area: molecular electronics;
    BibTeX:
    @article{Chen2012a,
      author = {Chen, L.N. and Cao, C. and Wu, X.Z. and Ma, S.S. and Huang, W.R. and Xu, H.},
      title = {Effects of partial hydrogenation on electronic transport properties in C60 molecular devices},
      journal = {Solid State Communications},
      year = {2012},
      volume = {152},
      number = {23},
      pages = {2123--2127},
      url = {http://www.sciencedirect.com/science/article/pii/S0038109812005315},
      doi = {http://dx.doi.org/10.1016/j.ssc.2012.09.011}
    }
    
    Guomin Ji, Yuqing Xu, Bin Cui, Changfeng Fang, Xiangru Kong, Dongmei Li & Desheng Liu Rectifying behaviors of an Au/(C20)2/Au molecular device induced by the different positions of gate voltage 2012 RSC Advances
    Vol. 2(30), 11349-11353 
    DOI  
    Abstract: The electronic transport properties of a gated Au/(C20)2/Au molecular device are studied using nonequilibrium Green's function in combination with density functional theory. The results show that different applied positions of the external transverse gate voltage can effectively tune the current-voltage (I-V) characteristic of molecular devices. Rectifying behaviors of the device can be realized when the gate voltage is applied asymmetrically on the left C20 molecule, and the rectification directions can also be modulated by the positive or negative value of the gate voltage. These results provide an important theoretical support to experiments and the design of a molecular rectifier.
    Keywords: ATK; Application; molecular electronics; fullerenes; rectification
    Area: molecular electronics; fullerenes
    BibTeX:
    @article{Ji2012a,
      author = {Ji, Guomin and Xu, Yuqing and Cui, Bin and Fang, Changfeng and Kong, Xiangru and Li, Dongmei and Liu, Desheng},
      title = {Rectifying behaviors of an Au/(C20)2/Au molecular device induced by the different positions of gate voltage},
      journal = {RSC Advances},
      publisher = {The Royal Society of Chemistry},
      year = {2012},
      volume = {2},
      number = {30},
      pages = {11349--11353},
      doi = {http://dx.doi.org/10.1039/C2RA21146G}
    }
    
    Antonio J. Mota, Luis Ávarez de Cienfuegos, Sara P. Morcillo, Noelia Fuentes, Delia Miguel, Salvador Rodríguez-Bolívar, Francisco M. Gómez-Campos, Diego J. Cárdenas & Juan M. Cuerva Thermally Driven Nanofuses Based on Organometallic Rotors 2012 ChemPhysChem
    Vol. 13(17), 3857-3865 
    DOI  
    Abstrac