  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.
