Modulating the thermal conductivity of silicon nanowires via surface amorphization

We perform non-equilibrium molecular dynamics calculations to study the heat transport in crystalline-core amorphous-shell silicon nanowires (SiNWs). It is found that the thermal conductivity of the core-shell SiNWs is closely related to the cross-sectional area ratio of amorphous shell. Through shell amorphization, an 80% reduction in thermal conductivity compared to crystalline SiNWs with the same size can be achieved, due to the non-propagating heat diffusion in the amorphous region. In contrast to the strong temperature-dependent thermal conductivity of crystalline SiNWs, the core-shell SiNWs only show weak temperature dependence. In addition, an empirical relation is proposed to accurately predict the thermal conductivity of the core-shell SiNWs based on the rule of mixture. The present work demonstrates that SiNWs with an amorphized shell are promising candidates for thermoelectric applications.