Modeling thermal conductivity in silicon nanowires

The complexity of heat transport in silicon nanowires (SiNWs) and, specifically, its dependence on temperature and the nanowire diameter, is beyond continuum models of heat conduction and necessitate consideration of atomic-level heat-conduction models. In this work, we specifically aim to ascertain the ability of models based on non-equilibrium statistical mechanics to reproduce the observed anisotropy, temperature and size dependence of the thermal conductivity of SiNWs. In this approach, the atomic-level kinetic relations are regarded as empirical and subject to modeling. Within this framework, we find that a simple model, based on the introduction of a thin amorphous layer at the surface of the SiNWs, yields effective thermal conductivities that are in excellent agreement with the experimental data over a range of temperatures and diameters.