Molecular dynamics analysis of spectral characteristics of phonon heat conduction in silicon

Abstract

Due to the technological significance of silicon, its heat conduction mechanisms have been studied extensively. However, there have been some lingering questions surrounding the phonon mean free path and importance of different polarizations. This research investigates phonon transport in bulk crystalline silicon using molecular dynamics and lattice dynamics. The interactions are modeled with the environment dependent interatomic potential (EDIP), which was designed to represent the bulk phases of silicon. Temperature and phonon frequency dependent relaxation times are extracted from the MD simulations and used to generate a detailed picture of phonon transport. It is found that longitudinal acoustic phonons have the highest contribution to thermal conductivity and that the phonon mean free path varies by orders of magnitude with respect to the phonon spectra. For relaxation times, we observe moderate anisotropy and good agreement with the frequency dependence predicted by scattering theories. We also find that phonons with mean free paths between .1 and 10 micron are responsible for 50% of the thermal conduction, while phonons with wavelengths less than 10 nanometers make up 80%.