Curvature dependence of electric and thermal conductivity in carbon nanotubes

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Curvature dependence of electric and thermal conductivity in carbon nanotubes

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Curvature dependence of electric and thermal conductivity in carbon nanotubes

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Curvature dependence of electric and thermal conductivity in carbon nanotubes

Wan-Ju Li

Phys 570X Proposal presentation

04/22/2009

- Motivation
- Introduction
- Conductivities under strain
- Summary

- Structure deformations are common in the growth of CNTs as well as in developing CNT-based nano devices.
- Dependences of electric and thermal conductivities on the radius of the CNTs and the curvature radius are essential for estimating the preperties of our designed nano device.

M: number of transport channels

G: electric conductance

E: energy of electrons

When E lies inside a band gap we can use quantum mechanical penetration or thermal activation transport to obtain the transmission coefficient and then get electric conductance.

J X Cao, X H Yan, J W Ding and D L Wang, J. Phys.: Condens. Matter 13 (2001) L271–L275

Liu Yang and Jie Han,

Phys.Rev.Lett. 5,154(2000)

E. D. Minot,et al (McEuen group) Phys.Rev.Lett.90.156401(2003)

- Computer Simulation
- Interatomic potential form
- Newtonian dynamics

Example of a molecular dynamics simulation in a simple system: deposition of a single Cu atom on a Cu (001) surface. Each circle illustrates the position of a single atom;

http://en.wikipedia.org/wiki/Molecular_dynamics

Potential form for our problem

Parameters, except R and D, are chosen to fit the cohesive energy, lattice constant, and bulk modulus of diamond. For carbon we choose R=1.95A D=0.15A, where R is chosen to include only the first neighbor shell.

J. Tersoff, PRB 37, 6991(1988)

Thermal conductivity λ is related to the thermal current correlation function.

Savas Berber, Young-Kyun Kwon,* and David Tománek, Phys.Rev.Lett.84,4613(2000)

r

R

- Tight binding model for band structure
- Add band gap modification
- Get electric conductance (conductivity) as a function of incident energy
- Also include effects of tube radius and curvature radius

r

R

- Specify the geometry under strain
- Molecule Dynamics simulation

Michael C H Wu and Jang-Yu Hsu,

nanotechnology 20 145401(2009)

- In order to predict the behaviors of designed nano devices it is necessary to understand the influence of curvature
- Electric conductivity-
Tight-binding model

+ change of gap by strain

- Thermal conductivity-
Molecule dynamics simulation

R. Heyd. et al, PRB 55,6820(1997)