Partially coherent phonon transport in two-dimensionally rough nanowires

Rough surface nanowires exhibit a severely reduced thermal conductivity compared to the bulk. Their thermal conductivities are much below the value predicted from the diffuse scattering model. Such low thermal conductivities are particularly promising for thermoelectric applications. We extend our previous work on understanding this phenomenon using a model of partially coherent phonon transport. Considering both azimuthal and longitudinal roughness, we show that it is the latter that dominates thermal conductivity reduction. Our work advanced fundamental phonon boundary scattering that is key in applications ranging from semiconductor devices to thermoelectric materials.