Effect of morphology on the phonon thermal conductivity of Si, Ge, and Si/Ge core/shell nanowires

Abstract

An additional factor in reducing thermal conductivity for thermoelectric applications of semiconductor nanowires is a change in morphology. In this paper, for Si, Ge and core/shell Si/Ge nanowires the effect of the volume fraction and the type of core material on thermal conductivity at 300 K is investigated by means of nonequilibrium molecular dynamics. Nanowires with experimentally observed <100>, <110>, <111> and <112> orientations and different cross sections were taken into account. It was found that for <112>-oriented Si-core/Ge-shell nanowires with a core volume fraction of ~30% the thermal conductivity is the lowest (5.76 W/(m · K)), while the thermal conductivity values for pure Si and Ge nanowires are 13.8 and 8.21 W/(m · K), respectively. Keywords: nanowire, core/shell structure, morphology, silicon, germanium, thermal conductivity, molecular dynamics.