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ABSTRACT: Electronic transport is among the unique physical phenomena whose applications have shaped human civilization as we know it
today. From old telegrams and light bulbs to modern televisions, mobile phones, laptops, and super-computers, all make use
of electronic transport. In fact, nowadays we can hardly find any significant technological product in which electronic transport
is not used one way or another. This enormous technological impact is a result of basic scientific research on electron tunneling
and scattering, in different environments and including various levels of interactions and correlations. The basic research
in the field of electronic transport is expected to yield equally unique, and even more important, fruits in future, as the
challenges of this vibrant field are ever increasing. One of the main areas of interest which has been the focus of numerous
scholarly works is electronic transport at nanometer length scales. The reason is that miniaturization of electronic components
has caused the device dimensions to reach nanoscale. At nanoscale, the atomistic character of the systems can no longer be
treated using rather rough models applicable at micrometer length scales. Therefore, fundamentally new approaches are necessary,
in both theory and experiment, to deal with electronic transport at nanoscale.
01/2008: pages 219-241;
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ABSTRACT: The quantum transport of a gated polythiophene nanodevice is analyzed using density functional theory and nonequilibrium Green's function approach. For this typical molecular field effect transistor, we prove the existence of two main features of electronic components, i.e., negative differential resistance and good switching. Ab initio based explanations of these features are provided by distinguishing fixed and shifting conducting states, which are shown to arise from the interface and functional molecule, respectively. The results show that proper functional molecules can be used in conjunction with metallic electrodes to achieve basic electronics functionality at molecular length scales.
The Journal of Chemical Physics 08/2007; 127(2):024901. · 3.33 Impact Factor
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ABSTRACT: The density functional theory and Green’s function approaches have been used for the investigation of the electronic and transport properties of bismuth nanowires deposited on a Si(001) surface. The results of calculations show that the conductance properties of deposited bismuth wires depend on the morphology of the silicon surface and the existence of dangling bonds on the surface, which may lead to current leakage across these bonds. Thus in order to use the bismuth lines as atom-wire interconnections for molecular electronics applications it is important to use the hydrogenated Si(001) surface. Despite the fact that Bi nanowires exhibit semiconductor features, the current through these nanowires can be operated within a given voltage region. Moreover Bi nanowires may possibly be used as a nanoline template for other metals.
Phys. Rev. B. 03/2007; 75(11).
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ABSTRACT: The geometry and electronic structures of metal 5, 15-di-(4-thiophenyl)-porphyrin (MDTP) have been investigated using first-principles calculations. Several metal atoms, including Cr, Mn, Fe, Co, Ni, Cu and Zn, have been selected. It has been found that the dihedral angle between porphyrin and thiophenyl planes is close to the perpendicular, which means that the π conjugation in whole MDTP molecules is broken. The most stable spin configurations of Cr, Mn, Fe, Co and NiDTPs are 5/2, 1, 1/2 and 0, respectively. Analysis of metal 3d-orbital splitting in Zn and NiDTP have shown that in the case of NiDTP, the out-of-plane interaction between metal 3d-orbitals and π orbital of porphyrin is larger than that in the case of ZnDTP. The results suggest that the Ni metal will enhance the conductance of DTP because transport properties in molecular systems have strong relations to the molecular π orbital.
Molecular Simulation 11/2004; 30(13-15):929-933. · 1.33 Impact Factor
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ABSTRACT: Using an approach different from the conventional vapor doping methods, Cs positive ions in a magnetized-plasma column are irradiated upon a negatively biased substrate which is covered with dispersed single-walled carbon nanotubes (SWNTs). The Cs ions are evidently observed inside SWNTs by the Z-contrast method in scanning transmission electron microscopy, demonstrating the formation of alkali-metal encapsulating SWNTs. Ab initio band structures and density of states for the light and heavy doping regimes indicate the possibility of using Cs-doped SWNTs as doped junctions, with potential application in nanoelectronics. This is supported by the direct experimental observation of an actual junction.
Phys. Rev. B. 08/2003; 68(7).
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08/2002;
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ABSTRACT: The massive-band effects on screening behavior of metallic carbon nanotubes are theoretically investigated using two different methods; continuous and lattice quantum theories. Both approaches show screening of a localized external perturbation with an effective screening length of the order of the nanotube diameter. Calculating the nonlinear deformation of the local density of states near the charged perturbation, we show that the perturbative effects of the massive bands are effectively canceled by direct massive band interactions, such that a good agreement between the two methods can be achieved. The effective screening is important in nanoscale integration of nanotube-based electronic devices.
06/2002;
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ABSTRACT: Transport properties of doped nanotube-based double junctions forming a nanotransistor are investigated within the tight binding
formalism. The effects of doping, gate length and gate-source hopping have been considered. It is found that in addition to
the importance of rotational symmetry in determining transport properties, large gains can be achieved for semiconducting
doped tubes.
The European Physical Journal D 09/2001; 16(1):353-355. · 1.48 Impact Factor
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Journal of Physical Chemistry C. 111(18):6690-6693.
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Japanese Journal of Applied Physics 49(11):5103. · 1.06 Impact Factor
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Applied Physics Letters 74:79. · 3.84 Impact Factor
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ABSTRACT: Recently, molecular electronics has attracted much attention as a ‘post-silicon technology’ for future nanoscale electronic devices. One of the most important elements in molecular electronic devices is the realization of a unimolecular rectifier. In the present study, the geometric and electronic structure of the TTF-derivative (donor)–sigma-bond–TCNQ-derivative (acceptor), a leading candidate for a molecular rectifying device has been investigated theoretically using ab initio quantum mechanical calculations.
Thin Solid Films · 1.89 Impact Factor
