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Tight-binding Model (tight-binding + model)

Distribution by Scientific Domains

Physics and Astronomy	71%

Selected Abstracts

A new approach for numerical simulation of quantum transport in double-gate SOI

INTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 6 2007
Tarek M. Abdolkader
Abstract Numerical simulation of nanoscale double-gate SOI (Silicon-on-Insulator) greatly depends on the accurate representation of quantum mechanical effects. These effects include, mainly, the quantum confinement of carriers by gate-oxides in the direction normal to the interfaces, and the quantum transport of carriers along the channel. In a previous work, the use of transfer matrix method (TMM) was proposed for the simulation of the first effect. In this work, TMM is proposed to be used for the solution of Schrodinger equation with open boundary conditions to simulate the second quantum-mechanical effect. Transport properties such as transmission probability, carrier concentration, and I,V characteristics resulting from quantum transport simulation using TMM are compared with that using the traditional tight-binding model (TBM). Comparison showed that, when the same mesh size is used in both methods, TMM gives more accurate results than TBM. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Tuning of electron transport through molecular bridge systems: A study of shot noise

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 1 2008
Santanu K. Maiti
Abstract We study electron transport characteristics through a single phenalenyl molecule attached with two nonsuperconducting electrodes by the use of Green's function technique. Parametric calculations are given based on the tight-binding model to characterize the electron transport through such molecular bridge system. It is observed that the electron transport properties are significantly influenced by (a) the interference effect and (b) the molecule-to-electrodes coupling strength. In this context we also describe the noise power of the current fluctuations that provides an important information about the electron correlation, which is obtained by calculating the Fano factor (F). The knowledge of this current fluctuations gives a key idea for fabrication of efficient molecular devices. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source]

Theoretical resonant Raman spectra of nanotube (7,0) with point defects

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 11-12 2009
Valentin N. Popov
Abstract The Raman spectra of the nanotube (7,0) with point defects (monovacancy, divacancy, and Stone,Wales defect) were simulated in order to derive spectroscopic signatures of defective nanotubes. First, we calculated the electronic band structure and the phonon dispersion of the defective nanotubes using supercells within a non-orthogonal tight-binding model. We found that new optical transitions and Raman-active phonons appeared in comparison with the perfect nanotube. Secondly, we calculated the resonance Raman excitation profile for all Raman-active phonons of the defective nanotubes and simulated their Raman spectra at specific laser excitation energies. The predicted high-intensity Raman lines can be used as spectroscopic signatures of the defective nanotubes. [source]

The low-energy electronic properties of graphene ribbons in spatially modulated magnetic fields

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 12 2008
J. Y. Wu
Abstract The low energy magnetoelectronic structures for a nanographene ribbon under modulated magnetic fields are investigated through the Peierls tight-binding model. They are dominated by the field strength, period, phase, the ribbon width, and edge structure. The modulated magnetic field could add state degeneracy, modify energy dispersions, alter subband spacings, affect carrier-density distributions, create additional band-edge states, and extend the partial flat bands. The main features of energy bands are directly reflected in density of states, such as the position, the height, the structure, and the number of the prominent peaks. These results are compared with a zigzag ribbon under a uniform magnetic field. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Theory of electronic structure of BGaAs and related alloys

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2008
A. Lindsay
Abstract Previous experiments on BxGa1,xAs containing a few percent boron show a dramatic increase in electron effective mass, m*e, similar to that observed in many GaNxAs1,x samples. By contrast, there is a near-linear blue-shift of the energy gap, which can be conventionally described using the virtual crystal approximation. We use a tight-binding model to show that isolated B atoms have little effect either on the band gap or lowest conduction band dispersion in BxGa1,xAs. By contrast, B pairs and clusters introduce defect levels close to the conduction band edge (CBE) which, through a weak band-anticrossing (BAC) interaction, significantly reduce the band dispersion in and around the , -point, thus accounting for the strong increase in m*e and reduction in mobility observed in these alloys. Calculations show that replacing gallium by aluminium shifts the CBE upwards, leading to a large density of B-related states in the energy gap. By contrast, indium shifts the band edge downwards, leading eventually to a band edge m*e close to that predicted by the virtual crystal approximation. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Quasiperiodic impurity energy spectra of GaAs/GaxAl1,xAs superlattices

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2004
M. S. Vasconcelos
Abstract In this work we consider a generalized Fibonacci quasiperiodic superlattice (GFQPSL), within a tight-binding model, in which its nearest-neighbor-hopping matrix elements are distributed according to the generalized Fibonacci sequence. The electronic density of states (DOS) is then determined by using a Green function method based on Dyson's equation together with a transfer-matrix treatment. The resulting energy spectrum is then determined, considering initial physical parameters according to the scheme used in the experimental realization of a GFQPSL. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Localization of excitons in weakly disordered semiconductor structures: A model study

ANNALEN DER PHYSIK, Issue 12 2009
N. Gögh
Abstract Localization of the center-of-mass (com) motion of an exciton in a disordered semiconductor structure is studied theoretically by focusing on nonlinear optical spectroscopy. A one-dimensional tight-binding model with diagonal disorder is applied and the Coulomb interaction is treated consistently. In the ordered situation the center-of-mass momentum (K) selection rule leads to only the lowest transition for K = 0. The break down of the com-K-selection rule produces the well known asymmetric excitonic lines of disordered semiconductors. The coupling between the lowest dominant transition to this modified com-continuum yields Fano-like features in the nonlinear spectra. [source]