Development of a Monte-Carlo Simulator for Phonon Transport in Nanocomposites
Date Issued
2009
Date
2009
Author(s)
Tsai, Tung-Chun
Abstract
A Monte-Carlo simulator is developed for phonon transport in nanostructured semiconductors, which solves the phonon Boltzmann transport equation under the single mode relaxation time (SMRT) approximation and the gray medium approximation. Physical models for phonon transmission/reflection at heterogeneous interfaces and numerical boundary conditions are properly designed. Most of all, we take advantage of the geometric symmetry that exists in a system to reduce the computational amount.n use of this MC solver, we investigate the phonon transport phenomena within Si/Ge and PbTe/PbTe superlattice thin films. The influences of the interface roughness, the superlattice period, and the layer thickness ratio on the phonon thermal conductivity are explored. The investigation results verify the thermal conductivity of superlattice thin films is strongly affected by the interface roughness and the interface density (interfacial area per volume). Especially, the influences of the interfaces perpendicular to the heat flow direction are much stronger than the parallel ones. Moreover, a minimum in-plane thermal conductivity is observed when the layer thickness ratio is varied with the superlattice period fixed. It arises from the influences of interface scattering on the layer thermal conductivity. Finally, it is found the analytic predictions and simulation results of the cross-plane thermal conductivity agree very well, but those of the in-plane thermal conductivity do not. It is explained by the discrepancies between the physical models in the analysis and in the simulation.
Subjects
Monte-Carlo simulation
phonon transport
gray medium approximation
interface roughness
superlattice thin film
thermal conductivity
Type
thesis
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