Electronic transport properties of carbon nanotoroids (original) (raw)
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International Journal of Quantum Chemistry, 2019
Density functional theory and molecular dynamics (MD) calculations were used to evaluate electronic structure properties in a series of nanotubes with smallest possible diameters (both types: armchair and zigzag), and the corresponding chiral nanotubes (8,m) for 0 ≤ m ≤ 8. The calculations were performed considering a length of 16.5 Å. We evaluated a set of 26 combinations of dual nanotubes (armchair/armchair, zigzag/zigzag, armchair/zigzag, and zigzag/armchair), where the first label corresponds to the outer tube. We extended our study with nine additional systems of double-walled carbon nanotubes (DWCNT) with semiconductor nature. In this regard, we gave insight into the semiconductive or metallic nature inherited to the dual tubes. DWCNT systems were possible to construct by maintaining a radial distance of 3.392 Å for the armchair/armchair arrangement and 3.526 Å for the zigzag/zigzag type. It was considered as a reference, the interplanar distance of graphite (3.350 Å). Electronic transport calculations were also performed on selected DWCNT systems in order to understand the role played by the different symmetries under study. It was evidenced that the electronic structure nature of the systems rules the ability to transport electrons through the DWCNT interface.
Electronic structure and quantum transport in carbon nanotubes
Applied Physics A: Materials Science & Processing, 1998
The electrical properties of various forms of carbon nanotubes are presented with particular emphasis placed on individual multi-wall and single-wall tubes. After a brief survey of the electronic structure of single-wall carbon nanotubes, electronic transport mechanisms are overviewed in relation with the dimensionality of the carbon system. Typical quantum aspects of low temperature electronic conduction for low dimensionality encountered in some carbon nanotubes are discussed.
Study of electronic transport mechanism in carbon nanobuds (CNBs) using first-principles approach
In the present work we have investigated the electronic transport properties of fullerene functionalized single wall carbon nanotube (14,0) i.e. the carbon nanobuds (CNBs) with two different configurations using the first-principles density functional-based non-equilibrium Green function (NEGF) method. Our findings show that the localized states developed in the vicinity of bud region cause strong back-scattering and reduce the electron transmission significantly in the entire energy region. The I-V characteristics of the pristine CNT(14,0) show that it is semiconducting in nature with a threshold voltage 0.55 V. Upon fullerene functionalization of CNT (formation of small neck carbon nanobud) the threshold voltage changes to 0.60V. However on functionalization with long neck (6,0), no noticeable change in threshold voltages is observed. It has been further ascertained from I-V characteristic plots that zigzag nanotubes upon nanobud formation do not change their semiconducting nature. CNBs are promising candidates for nano electronics as they can enhance the cold field emission due to their charge distribution profile which extends from tube to the bud region.
Conductance through a single impurity in the metallic zigzag carbon nanotube
Applied Physics Letters, 2009
We investigate transport through a single impurity in metallic zigzag carbon nanotube and find the conductance sensitively depends on the impurity strength and the bias voltage. It is rather interesting that interplay between the current-carrying scattering state and evanescent modes leads to rich phenomena including resonant backward scattering, perfect tunneling and charge accumulations. In addition, we also find a dual relation between the backscattered conductance and the charge accumulation. At the end, relevance to the experiments is discussed.
Magnetic-field effects on transport in carbon nanotube junctions
2007
Here we address a theoretical study on the behaviour of electronic states of heterojunctions and quantum dots based on carbon nanotubes under magnetic fields. Emphasis is put on the analysis of the local density of states, the conductance, and on the characteristic curves of current versus voltage. The heterostructures are modeled by joining zigzag tubes through single pentagon-heptagon pair defects, and described within a simple tight binding calculation. The conductance is calculated using the Landauer formula in the Green functions formalism. The used theoretical approach incorporates the atomic details of the topological defects by performing an energy relaxation via Monte Carlo calculation. The effect of a magnetic field on the conductance gap of the system is investigated and compared to those of isolated constituent tubes. It is found that the conductance gap of the studied CNHs exhibits oscillations as a function of the magnetic flux. However, unlike the pristine tubes case, they are not Aharonov-Bohm periodic oscillations.
Transfer-matrix simulations of electronic transport in single-wall and multi-wall carbon nanotubes
Carbon, 2005
We present simulations of electronic transport in single-wall and multi-wall carbon nanotubes, which are placed between two metallic contacts. We consider situations where the electrons first encounter a singe-wall nanotube (corresponding to either the inner or the outer shell of the (10, 10)@(15, 15)@(20, 20) and (10, 10)@(20, 10)@(20, 20) nanotubes), before encountering the multi-wall structures. The role of this two-step procedure is to enforce the electrons to enter a single shell of the multi-wall nanotubes, and we study how from that point they get redistributed amongst the other tubes. Because of reflections at the metallic contacts, the conductance of finite armchair nanotubes is found to depend on the length of the tubes, with values that alternate between three separate functions. Regarding the transport in multi-wall nanotubes, it is found that the electrons keep essentially propagating in the shell in which they are initially injected, with transfers to the other tubes hardly exceeding one percent of the whole current. In the case where the three tubes are conducting, these transfers are already completed after four nanometers. The conductance and repartition of the current present then oscillations, which are traced to the band structure of the nanotube. The transfers between the shells and the amplitude of these oscillations are significantly reduced when the intermediate tube is semiconducting.
Electrical conductance of carbon nanotori in contact with single-wall carbon nanotubes
Journal of Applied Physics, 2004
The realization of the potential of carbon nanotori as elements of nanoscale devices based on their recently predicted unusual properties requires a thorough understanding of contacting these nanostructures. We carried out a series of calculations of the electric conductance of carbon nanotori contacted by single-wall carbon nanotubes to shed light on the effects of the geometry as well as the chemistry of the contacts. The relaxed structures of the contacted nanotori were determined by an order-N nonorthogonal tight-binding molecular dynamics scheme. The conductance was calculated using the Landauer-Büttiker formula based on a -orbital Hamiltonian. We found that the conductance of the contacted carbon nanotorus is very sensitive to the transparency (chemistry) of the contacts. We also found that the equivalence (chemistry as well as geometry) of the contacts plays an important role in the transport properties. For example, a difference in the right contact and left contact will diminish the constructive quantum interference of the transmission as compared to the situation when the two contacts are equivalent. This conclusion is general and is expected to be applicable for any metallic contacts to the contacted carbon nanotori.
Electrical Transport in Single-Wall Carbon Nanotubes
We review recent progress in the measurement and understanding of the electrical properties of individual metal and semiconducting single-wall carbon nanotubes. The fundamental scattering mechanisms governing the electrical transport in nanotubes are discussed, along with the properties of p-n and Schottkybarrier junctions in semiconductor tubes. The use of advanced nanotube devices for electronic, high-frequency, and electromechanical applications is discussed. We then examine quantum transport in carbon nanotubes, including the observation of quantized conductance, proximity-induced supercurrents, and spin-dependent ballistic transport. We move on to explore the properties of single and coupled carbon-nanotube quantum dots. Spin and orbital (isospin) magnetic moments lead to fourfold shell structure and unusual Kondo phenomena. We conclude with a discussion of unanswered questions and a look to future research directions.
Interference effects in electronic transport through metallic single-wall carbon nanotubes
Physical Review B, 2002
In a recent paper Liang et al. [Nature 411, 665 (2001)] showed experimentally, that metallic nanotubes, strongly coupled to external electrodes, may act as coherent molecular waveguides for electronic transport. The experimental results were supported by theoretical analysis based on the scattering matrix approach. In this paper we analyze theoretically this problem using a real-space approach, which makes it possible to control quality of interface contacts. Electronic structure of the nanotube is taken into account within the tight-binding model. External electrodes and the central part (sample) are assumed to be made of carbon nanotubes, while the contacts between electrodes and the sample are modeled by appropriate on-site (diagonal) and hopping (off-diagonal) parameters. Conductance is calculated by the Green function technique combined with the Landauer formalism. In the plots displaying conductance vs. bias and gate voltages, we have found typical diamond structure patterns, similar to those observed experimentally. In certain cases, however, we have found new features in the patterns, like a double-diamond sub-structure.
Electronic and transport properties of nanotubes
Reviews of Modern Physics, 2007
This article reviews the electronic and transport properties of carbon nanotubes. The focus is mainly theoretical, but when appropriate, the relation with experimental results is mentioned. While simple band-folding arguments will be invoked to rationalize how the metallic or semiconducting character of nanotubes is inferred from their topological structure, more sophisticated tight-binding and ab initio treatments will be introduced to discuss more subtle physical effects, such as those induced by curvature, tube-tube interactions or topological defects. The same approach will be followed for transport properties. The fundamental aspects of conduction regimes and transport length scales will be first briefly presented using simple models of disorder, with the derivation of a few analytic results concerning specific situations of short and long range static perturbations. Further, the latest developments in semi-empirical or ab initio simulations aiming at exploring the effect of realistic static scatterers (chemical impurities, adsorbed molecules, etc.) or inelastic electron-phonon interactions, will be emphasized. Finally, specific issues, going beyond the noninteracting electron model, will be addressed, including excitonic effects in optical experiments, the Coulomb blockade regime, and the Luttinger liquid, charge density waves or superconducting transitions.