Phonon-bond strength imperfection scattering mechanism in nanostructures

Abstract: Because of high surface-to-volume ratio, the most prominent size effect limiting thermal transport originates from phonon-surface scattering in nanostructures. Herein we propose the mechanism of phonon scattering by the bond strength imperfections on surface of nanostructures, and derive the phonon scattering rate of this mechanism by quantum perturbation theory combining with bond order theory. By incorporating this phonon-surface scattering mechanism to phonon Boltzmann transport equation, we calculate the thermal conductivity of silicon thin films and silicon nanowires, and find that the calculated results by our model are more close to the experimental data than those by classical phonon-boundary scattering model. Our findings are helpful not only for understanding the mechanism of phonon-surface scattering, but also for manipulating thermal transport in nanostructures by surface engineering.