Temperature dependence of the anharmonic decay of optical phonons in carbon nanotubes and graphite (original) (raw)
Related papers
Hot optical phonon decay in carbon nanotubes
Applied Physics Letters, 2008
We simulate hot optical phonon decay in small diameter ͑Ͻ0.7 nm͒ carbon nanotubes, solving the phonon Boltzmann transport equation using Monte Carlo methods incorporating the full phonon spectrum and phonon-phonon scattering. Results indicate decay times inversely proportional to the lattice temperature with negligible dependence on hot phonon polarization/wave vector or nanotube diameter and chirality. Nonequilibrium optical phonons with energies of ϳ0.2 eV decay by emitting two ϳ0.1 eV optical phonons, corresponding to out-of-plane polarization modes in graphitic materials. Modes polarized perpendicular to the nanotube axis may allow manipulation of hot phonon effects by the near environment of the nanotube.
Phonon-phonon interactions in single-wall carbon nanotubes
2006
The lifetime of phonon modes undergoing three-phonon interactions in single-wall carbon nanotubes has been calculated. The calculations are based upon an approach using Fermi's golden rule and a quasielastic continuum model for the anharmonic potential. In deriving the relaxation-rate equation, the effects of both normal and umklapp processes have been included, and a clear distinction between class 1 and class 2 events is made. Dispersion relations for the phonon modes of a carbon nanotube were obtained from analytic expressions developed by Zhang et al. The lifetime of the lowest two optical modes is found to be comparable to the lifetime of the acoustic modes. The results show that the relaxation rate is dominated by normal processes at low temperatures and umklapp processes at room temperature and above. A linear relationship between the relaxation rate and temperature is obtained for temperatures greater than 200 K. The relaxation-rate contribution decreases ͑increases͒ with an increase in the tube radius for normal ͑umklapp͒ processes. These results are suggested to have interesting implications for mean-free-path and thermal-conductivity calculations.
Loading Preview
Sorry, preview is currently unavailable. You can download the paper by clicking the button above.