Monte Carlo simulation of phonon transport in variable cross-section nanowires

A dedicated Monte Carlo (MC) model is proposed to investigate the mechanism of phonon transport in variable cross-section silicon nanowires (NWs). Emphasis is placed on understanding the thermal rectification effect and thermal conduction in tapered cross-section and incremental cross-section NWs. In the simulations, both equal and unequal heat input conditions are discussed. Under the latter condition, the tapered cross-section NW has a more prominent thermal rectification effect. Additionally, the capacity of heat conduction in the tapered cross-section NW is always higher than that of the incremental one. Two reasons may be attributed to these behaviors: one is their different boundary conditions and the other is their different volume distribution. Although boundary scattering plays an important role in nanoscale structures, the results suggest the influence of boundary scattering on heat conduction is less obvious than that of volume distribution in NWs with variable cross-sections.