Electrical Transport Properties of Carbon Nanotube Metal-Semiconductor Heterojunction

2016 ◽  
Vol 15 (05n06) ◽  
pp. 1660009 ◽  
Author(s):  
Keka Talukdar ◽  
Anil Shantappa
Keyword(s):  
Electrical Transport ◽  
Nearest Neighbor ◽  
Electronic Devices ◽  
Tight Binding ◽  
Transmission Function ◽  
Topological Defects ◽  
Dynamics Simulation ◽  
Internal Stresses ◽  
Electrical Transport Properties ◽  
Tight Binding Approximation

Carbon nanotubes (CNTs) have been proved to have promising applicability in various fields of science and technology. Their fascinating mechanical, electrical, thermal, optical properties have caught the attention of today’s world. We have discussed here the great possibility of using CNTs in electronic devices. CNTs can be both metallic and semiconducting depending on their chirality. When two CNTs of different chirality are joined together via topological defects, they may acquire rectifying diode property. We have joined two tubes of different chiralities through circumferential Stone–Wales defects and calculated their density of states by nearest neighbor tight binding approximation. Transmission function is also calculated to analyze whether the junctions can be used as electronic devices. Different heterojunctions are modeled and analyzed in this study. Internal stresses in the heterojunctions are also calculated by molecular dynamics simulation.

Effect of boron impurity in a carbon nanotube superlattice

2017 ◽  
Vol 31 (14) ◽  
pp. 1750106
Author(s):  
Zahra Karimi Ghobadi ◽  
Aliasghar Shokri ◽  
Sonia Zarei
Keyword(s):  
Carbon Nanotube ◽  
Band Structure ◽  
Boron Atom ◽  
Density Of States ◽  
Nearest Neighbor ◽  
Electronic Band Structure ◽  
Tight Binding ◽  
Topological Defects ◽  
Electronic Band ◽  
Neighbor Approximation

In this work, the influence of boron atom impurity is investigated on the electronic properties of a single-wall carbon nanotube superlattice which is connected by pentagon–heptagon topological defects along the circumference of the heterojunction of these superlattices. Our calculation is based on tight-binding [Formula: see text]-electron method in nearest-neighbor approximation. The density of states (DOS) and electronic band structure in presence of boron impurity has been calculated. Results show that when boron atom impurity and nanotube atomic layers have increased, electronic band structure and the DOS have significant changes around the Fermi level.

scholarly journals Tight–Binding Analysis of Electronic Structure of Germanene Sheet and Nanoribbons Including Stone-Wales Defect

2021 ◽  
Author(s):  
Komeil Rahmani ◽  
Saeed Mohammadi
Keyword(s):  
Band Structure ◽  
Band Gap ◽  
Energy Band ◽  
Dirac Point ◽  
Tight Binding ◽  
Topological Defects ◽  
Energy Band Structure ◽  
Fermi Velocity ◽  
Tight Binding Approximation ◽  
Wales Defect

Abstract In this paper, we investigate the electronic characteristics of germanene using the tight binding approximation. Germanene as the germanium-based analogue of graphene has attracted much research interest in recent years. Our analysis is focused on the pristine sheet of germanene as well as defective monolayer. The Stone-Wales defect, which is one of the most common topological defects in such structures, is considered in this work. Not only the infinite sheet of germanene but also the germanene nanoribbons in different orientations are analyzed. The obtained results show that applying the Stone–Wales defect into the germanene monolayer changes the energy band structure; the E-k curves around the Dirac point are no longer linear, a band gap is opened, and the Fermi velocity is reduced to half of that of defect-free germanene. In the case of nanoribbon structures, the armchair germanene nanoribbons with nanoribbon widths of 3p and 3p+1 reveal the semiconductor behaviour. However, armchair germanene nanoribbon with width of 3p+2 is semi-metal. After applying the Stone–Wales defect, the band gap of armchair germanene nanoribbons with widths of 3p and 3p+1 is reduced and it is increased for the width of 3p+2. Furthermore, there is no band gap in the energy band structure of zigzag germanene nanoribbon and the metallic behaviour is obvious.

New route to enhanced figure of merit at nano scale: effect of AAH modulation

2021 ◽  
Author(s):  
Moumita Dey ◽  
Suvendu Chakraborty ◽  
Santanu K Maiti
Keyword(s):  
Figure Of Merit ◽  
Nearest Neighbor ◽  
Tight Binding ◽  
Thermal Conductance ◽  
Transmission Function ◽  
Energy Conversion Efficiency ◽  
Thermoelectric Efficiency ◽  
Thermoelectric Energy ◽  
Large Figure ◽  
First Time

Abstract We report, for the first time, the phenomenon of thermoelectricity at quantum level considering a correlated disordered tight-binding (TB) one-dimensional lattice where site energies and/or nearest-neighbor hopping integrals are modulated in the cosine form following the well known Aubry-Andre-Harper (AAH) model. The atypical gapped and fragmented energy spectrum yields a transmission function whose steepness is not symmetrical around Fermi energy, and because of this fact, we obtain a reasonably large figure of merit, a quantity that measures the thermoelectric energy conversion efficiency. The efficiency can be further monitored by means of AAH phase(s) which undoubtedly gives a possible route of designing controlled thermoelectric devices. Evaluating transmission probabilities using the Green's function formalism, we compute all the thermoelectric quantities based on the Landauer integrals. The diagonal, off-diagonal and generalized versions of the AAH model are taken into account, and in all the cases we find favorable thermoelectric response. At the end of our analysis, we discuss briefly the specific role of phonon thermal conductance on thermoelectric efficiency to make the present investigation a self-contained one. Our theoretical study may shed some light in analyzing thermoelectric phenomena in similar kind of quasicrystals and other related systems.

Empirical Tight-Binding Applied to Silicon Nanoclusters

1997 ◽  
Vol 491 ◽  
Author(s):  
G. Allan ◽  
C. Delerue ◽  
M. Lannoo
Keyword(s):  
Band Structure ◽  
Nearest Neighbor ◽  
Good Description ◽  
Tight Binding ◽  
Localized States ◽  
Basis Set ◽  
Band Structure Calculation ◽  
Minimal Basis ◽  
Tight Binding Approximation ◽  
Bulk Band

ABSTRACTThe calculation of the electronic structure of silicon nanostructures is used to discuss the accuracy of results obtained by the tight-binding method. We first show that the level of refinement of the tight-binding approximation must be adapted to the calculated property. For example, an accurate description of both the valence and conduction bands which can be achieved with a 3rd-nearest neighbor approximation is necessary to calculate the variation of the gap energy with the silicon crystallite size. The sp3s* model which gives a bad description of the conduction band underestimates the confinement energy but can give good results when it is used to determine the variation of the crystallite band gap with pressure. To study Si-III (BC-8) nanocrystallites, we show that a good description of the bulk band structure can be obtained with non-orthogonal tight-binding but due to the large number of nearest neighbors one must take analytical variations of the parameter with interatomic distances. The parameters involved in these expressions can be easily fitted to the bulk band structures using the k-point symmetry without requiring the use of group theory. Finally we discuss the effect of increasing the size of the minimal-basis set and we show that it would be possible to get the values of the tight-binding parameters from a first-principles localized states band structure calculation avoiding the fit to the energy dispersion curves.

Electromechanical Behavior of Single and Multiwall Carbon Nanotubes

2008 ◽  
Vol 54 ◽  
pp. 390-395
Author(s):  
Antonio Pantano
Keyword(s):  
Carbon Nanotubes ◽  
Finite Element ◽  
Electrical Transport ◽  
Mixed Finite Element ◽  
Tight Binding ◽  
Multiwall Carbon Nanotubes ◽  
Building Blocks ◽  
Electrical Transport Properties ◽  
Electromechanical Behavior ◽  
Structural Deformations

Carbon nanotubes (CNTs) can be metallic or semiconductors depending simply on geometric characteristics. This peculiar electronic behavior, combined with high mechanical strength, make them potential building blocks of a new nano-electronic technology. High resolution images of CNTs often disclose structural deformations such as bent, twisted, or collapsed tubes. These deformations break the tube symmetry, and a change in their electronic properties should result. A computationally effective mixed finite element-tight-binding approach able to simulate the electromechanical behavior of single and multiwall nanotubes used in nano-electronic devices is presented. The finite element (FE) computes the evolution of atomic coordinates with deformation and provides these coordinates to a tight-binding (TB) code, enabling computation and updating of the electrical conductivity. The TB code is engineered to realize dramatic computational savings in calculating deformation-induced changes in electrical transport properties of the nanotubes.

LOCAL ELECTRONIC STRUCTURE OF Tl2Ca2Ba2Cu3O10 AND COMPARISON WITH LA-OXIDES AND Y-OXIDES

1990 ◽  
Vol 04 (09) ◽  
pp. 1537-1549 ◽  
Author(s):  
HUAI-YU WANG ◽  
FU-SUI LIU ◽  
EN-GE WANG ◽  
CHONG-YU WANG
Keyword(s):  
Electronic Structure ◽  
Nearest Neighbor ◽  
Tight Binding ◽  
The Other ◽  
Tight Binding Approximation ◽  
Densities Of States ◽  
Local Electronic Structure ◽  
Electronic Densities

Local electronic densities of states of Tl 2 Ca 2 Ba 2 Cu 3 O 10 (2223) are calculated by tight-binding approximation. The nearest and the next-nearest neighbor transitions are considered, and the results are compared with each other. After the latter is considered, the densities of states are smoothened and the semiconductor-like characteristic of the Tl-O layers disappears. Through comparison of 2223 with the other two high Tc ceramics La 2−x Sr x CuO 4 and YBa 2 Cu 3 O 7−x, it is believed that they have the same leading superconductive mechanism besides inter-plane interactions.

scholarly journals Conductance of Single- and Double-Gated Quantum Stub Transistor

2004 ◽  
Vol 1 (2) ◽  
pp. 36-40
Author(s):  
Alexandre B. Guerra ◽  
Edval J. P. Santos
Keyword(s):  
Low Power ◽  
Quantum Computation ◽  
High Frequency ◽  
Nearest Neighbor ◽  
Electronic Devices ◽  
Tight Binding ◽  
Electrical Behavior ◽  
Spin Polarized ◽  
Polarized Transport ◽  
Spin Polarized Transport

Quantum stub transistors are low power, high frequency, and nanometer-size devices, and as such they are candidates for next generation electronic devices. In particular, such structures may be used in spintronics-based quantum computation, because of its ability to induce spin-polarized transport. In this paper, we present the simulation of the conductance of the quantum stub transistor (single and double-gated), modeled with a nearest-neighbor tight-binding Hamiltonian. The results suggest how the electrical behavior of the quantum stub transistor may be improved.

scholarly journals Thermo-Electrical Conduction of the 2,7-Di([1,1′-Biphenyl]-4-yl)-9H-Fluorene Molecular System: Coupling between Benzene Rings and Stereoelectronic Effects

Molecules ◽  
2020 ◽  
Vol 25 (14) ◽  
pp. 3215 ◽  
Author(s):  
Judith Helena Ojeda Silva ◽  
Juan Sebastián Paez Barbosa ◽  
Carlos Alberto Duque Echeverri
Keyword(s):  
Electrical Transport ◽  
Quantum Noise ◽  
Molecular System ◽  
Tight Binding ◽  
Electrical Conductance ◽  
Thermal Conductance ◽  
Fano Factor ◽  
Aromatic System ◽  
Electrical Transport Properties ◽  
Benzene Rings

Theoretical and analytical thermal and electrical properties are studied through the 2,7-Di([1,1′-biphenyl]-4-yl)-9H-fluorene aromatic system as a prototype of a molecular switch. Variations of the dihedral angles between the two Benzene rings at each end of the molecule have been considered, thus determining the dependence on the structural variation of the molecule when the aromatic system is connected between metal contacts. The molecule is modeled through a Tight-Binding Hamiltonian where—from the analytical process of decimation and using Green’s functions—the probability of transmission (T) is calculated by using the Fisher–Lee relationship. Consequently, the thermal and electrical transport properties such as I − V curves, quantum noise (S), Fano factor (F), electrical conductance (G), thermal conductance ( κ ), Seebeck coefficient (Q), and merit number ( Z T ) are calculated. The available results offer the possibility of designing molecular devices, where the change in conductance or current induced by a stereoelectronic effect on the molecular junctions (within the aromatic system) can produce changes on the insulating–conductive states.

BAND STRUCTURE OF RHOMBOHEDRAL GRAPHITE

1958 ◽  
Vol 36 (3) ◽  
pp. 352-362 ◽  
Author(s):  
R. R. Haering
Keyword(s):  
Band Structure ◽  
Fermi Surface ◽  
Nearest Neighbor ◽  
Tight Binding ◽  
Rhombohedral Structure ◽  
Hexagonal Prism ◽  
Exchange Integral ◽  
Tight Binding Approximation ◽  
Out Of Plane ◽  
Bernal Stacking

The band structure of rhombohedral graphite has been investigated using the nearest-neighbor tight-binding approximation. The resulting behavior of the π-bands near the Fermi surface is more complex than in the case of the Bernal stacking. The two π-bands still touch, but the touching points no longer lie on the edges of a hexagonal prism in k-space. Instead, they lie on cylinders whose axes are the edges of the hexagonal prism. The radii of these cylinders are proportional to γ1, the nearest "out-of-plane" exchange integral. The de Haas – Van Alphen effect in the rhombohedral structure may be expected to yield useful information about the magnitude of γ1.

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