The effect of the electron–phonon coupling on the thermal conductivity of silicon nanowires

Abstract

The thermal conductivity of free-standing silicon nanowires (SiNWs) with diameters from 1–3 nm has been studied by using the one-dimensional Boltzmann’s transport equation. Our model explicitly accounts for the Umklapp scattering process and electron–phonon coupling effects in the calculation of the phonon scattering rates. The role of the electron–phonon coupling in the heat transport is relatively small for large silicon nanowires. It is found that the effect of the electron–phonon coupling on the thermal conduction is enhanced as the diameter of the silicon nanowires decreases. Electrons in the conduction band scatter low-energy phonons effectively where surface modes dominate, resulting in a smaller thermal conductivity. Neglecting the electron–phonon coupling leads to overestimation of the thermal transport for ultra-thin SiNWs. The detailed study of the phonon density of states from the surface atoms and central atoms shows a better understanding of the nontrivial size dependence of the heat transport in silicon nanowire.