The Effect of Cross-sectional Geometry on ZT Enhancement in Rough Silicon Nanostructures

Abstract

The dramatic reduction in the thermal conductivity of rough silicon nanowires is due to phonon localization in the wire resulting from multiple scattering of phonons from the rough walls. We report the dependence of thermal conductivity of the nanowires as a function of the surface roughness and the diameter of the wire by modeling the nanowire as a waveguide. In addition, we estimate the impact of boundary condition, dimensionality and cross section of rough wire on the thermal conductivity. This theoretical model gives insights for tailoring thermal conductivity and enhancing the ZT of silicon to 1 for its use in thermoelectrics.