Surface morphology and strain coupling effects on phonon transport in silicon nanowires

Abstract

We perform non-equilibrium molecular dynamics calculations to study the coupling effects of surface, defects, and strain on heat transport in silicon nanowires (SiNWs). It is found that, for single-crystalline SiNWs, rippled surface and vacancy defects can significantly reduce the thermal conductivity κ of SiNWs. In addition, through surface amorphization, the thermal conductivity can be further remarkably reduced, due to strong phonon scattering at the interface as well as the non-propagating diffusion of phonons in the amorphous region. However, the κ value of amorphous-surface SiNWs is not sensitive to the roughness and vacancy in amorphous surface. Besides surface and defects, it has been observed that stress-induced defects/deforms can introduce additional mechanism of phonon scattering, which decrease the thermal conductivity. The present work demonstrates that, through phonoic engineering to tune the thermal conductivity, SiNWs can be promising candidates for thermoelectric applications.