Uniaxial-stress effects on the electronic properties of carbon nanotubes (original) (raw)
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Metal–semiconductor transitions under uniaxial stress for single- and double-walled carbon nanotubes
Journal of Physics and Chemistry of Solids, 2001
The alignment defects observed in cylindrical carbon nanotubes are related to the band gaps in a 1-D tight binding scheme. The in¯uence of uniaxial stress on the electronic properties is analyzed and evidence is put forward of possible experimentally observable semiconductor to metal transitions under compression for single-and double-walled nanotubes. q
Computational Materials Science, 2004
Carbon nanotubes (CNTs) have been attracting attention because they have characteristic mechanical and electronic properties. It has been reported that single-walled CNTs can induce large deformation without bond breaking. Therefore, it is of interest to elucidate the electronic properties of CNTs under large deformation. We investigate the deformation behavior and the change in the electronic properties of zigzag-type single-walled CNTs with chiral vectors of (8,0), (12,0) and (14,0) under radial compression with semi-empirical band calculations based on the tight-binding method. The resistance against the deformation increases with the deformation, and its behavior depends on the diameter of the CNTs. The CNTs, which have band gap energy at the initial state, become metallic by the compression.
Electronic properties of zigzag and armchair carbon nanotubes under uniaxial strain
Journal of Applied Physics, 2008
Molecular dynamics simulations and quantum transport theory are employed to study the electronic properties of various zigzag and armchair carbon nanotubes ͑CNTs͒ under uniaxial compressive and tensile strains. It is found that the transfer integral decreases as the tensional strain increases. Furthermore, in the ͑3N +1,0͒ and ͑3N ,0͒ zigzag nanotubes, the current induced by the application of a suitable bias voltage varies linearly with the magnitude of the applied strain. Thus, these particular zigzag CNTs are suitable for use as nanoscale strain sensors. Furthermore, the wider detected ranges occur in the smaller diameter of ͑3N ,0͒ and ͑3N +1,0͒ tubes. However, in ͑11,0͒ zigzag nanotube and ͑5,5͒ armchair nanotube, the variation in current is not in accordance with Ohm's law with respect to variations in the applied strain. Specifically, the electronic resistance decreases with increasing strain in ͑11,0͒ zigzag nanotube, while the current variations in different strains show the irregular and small perturbation in ͑5,5͒ armchair nanotube. Accordingly, neither the ͑11,0͒ zigzag nanotube nor the ͑5,5͒ armchair nanotube is suitable for strain sensing applications, but the ͑5,5͒ armchair nanotube has a current with the stable property for a conducting wire.
Electronic Properties of Strained Carbon Nanotubes: Impact of Induced Deformations
The Journal of Physical Chemistry C, 2015
In order to resolve quantitative mismatch between measurements and the existing theory, we perform systematic theoretical study of the effects of small uniform strain on the electronic properties of single-wall carbon nanotubes. Applied torsion or uniaxial strain induces structural deformations (shifts of the two sublattices, radial and torsional strains induced by the applied uniaxial strain, e.g.) which lead to significantly weaker impact on electronic properties of the strained tube. This damping is more pronounced for torsion. For instance, in tubes with chiral angle close to 30 • , the band gap change is reduced up to 60%. Dominant attenuating factor is the relative shift of the sublattices along the tube axis, manifesting strong electronic coupling with the longitudinal highenergy Raman mode. Obtained results match better the experimental observation of the shifts of optical transitions energies and the gauge factor in carbon nanotube based piezoresistive sensors, giving a base for further device development.
Physical Review B, 2007
The electron-phonon interactions determine the temperature dependent photoluminescence of semiconducting carbon nanotubes. Both effects, the energy shifts and spectral narrowing of the transitions, can be attributed to the electron-phonon interaction. In this paper, we present an accurate measurement of the temperature induced broadening of the photoluminescence transitions of carbon nanotubes, and model this broadening in terms of the theory, previously used to model the thermal broadening of critical points in conventional semiconductors. Through this fitting procedure, parameters could be estimated which provide important insight into the strength of the electron-phonon interactions. Moreover, careful studies of the energy shifts induced by the external strain had revealed a n − m family behavior. We further conclude that using a mathematical expression that combines the theory of semiconducting carbon nanotubes under hydrostatic pressure and strain, this family behavior observed experimentally could be theoretically reproduced, providing tools to model and predict the effect of strain on the electronic properties of carbon nanotubes.
Effect of Strain on the Energy Band Gaps of (13, 0) and (15, 0) Carbon Nanotubes
The electronic energy band gap is a basic property of all semiconductors since it is responsible for the electrical transport and optical properties. Control of the size of the energy band gap is important in optimizing electronic devices. In this study, we have shown that the application of tensile strain modifies the size of the band gaps in semiconducting Single Walled Carbon Nanotubes (SWCNTs) and opens a band gap in metallic SWCNTs. We simulated (13,0) and (15,0) SWCNTs under various compressive and tensile strain at 300K. Pristine (13,0) SWCNT is a semiconductor with a band gap of 0.44 eV and (15,0) SWCNT is metallic. The strain was applied as both compression and stretching along the z-direction. The density of states are obtained in real space using a parallel Order N, Tight Binding Molecular Dynamic (O(N) TBMD) simulation code designed by Dereli et. al. [1-3].The energy band gaps of (13,0) and (15,0) SWCNTs demonstrate different behaviors with the presence of strain. For (13,0) tube, energy band gap decreases with negative strain values (compression) and the onset of semiconductor-metal transition occurs at a negative strain value of %8. For (15,0) SWCNT, application of positive and negative strains opens up the band gap causing metal-semiconductor transitions.
Electromechanical effects in carbon nanotubes: Ab initio and analytical tight-binding calculations
Physical Review B, 2003
We perform ab initio calculations of charged graphene and single-wall carbon nanotubes (CNTs). A wealth of electromechanical behaviors is obtained: (1) Both nanotubes and graphene expand upon electron injection. (2) Upon hole injection, metallic nanotubes and graphene display a nonmonotonic behavior: Upon increasing hole densities, the lattice constant initially contracts, reaches a minimum, and then starts to expand. The hole densities at minimum lattice constants are 0.3 |e|/atom for graphene and between 0.1 and 0.3 |e|/atom for the metallic nanotubes studied. Semiconducting CNTs with small diameters (d 20Å) always expand upon hole injection; (4) Semiconducting CNTs with large diameters (d 20Å) display a behavior intermediate between those of metallic and large-gap CNTs. The strain versus extra charge displays a linear plus powerlaw behavior, with characteristic exponents for graphene, metallic, and semiconducting CNTs. All these features are physically understood within a simple tight-binding total-energy model.
Structural and electronic properties of carbon nanotubes under hydrostatic pressures
Chinese Physics B, 2008
The bending of a carbon nanotube is studied by considering the structural evolution of a carbon nanotorus from elastic deformation to the onset of the kinks and eventually to the collapse of the walls of the nanotorus. The changes in the electronic properties due to non-local deformation are contrasted with those due to local deformation to bring out the subtle issue underlying the reason why there is only a relatively small reduction in the electrical conductance in the former case even at large bending angles while there is a dramatic reduction in the conductance in the latter case at relatively small bending angles.
Metallic–semiconducting transition of single-walled carbon nanotubes under high axial strain
Computational Materials Science, 2004
Carbon nanotubes (CNTs) have been attracting attention because of their characteristic mechanical and electronic properties. It has been pointed out that a single-walled CNT can stretch in the axial direction at 30% strain without any bonds breaking. Therefore, it is of interest to investigate electronic properties of CNTs under high axial strain. In this study, we investigate the change in electronic properties of single-walled CNTs under high axial strain with tightbinding semiempirical band calculations. The property of CNTs with the chiral vectors, (m; n); m À n ¼ 3q, where m, n and q are integers, shows the transition, metallic fi semiconducting fi metallic in that order under tension, except armchair tubes, which remain metallic. The transition in CNTs with the chiral vectors of m À n ¼ 3q þ 1 or m À n ¼ 3q þ 2 is: semiconducting fi metallic fi semiconducting, and the transient strain is dependent on the diameter of the CNTs.