Molecular dynamics simulation of the thermal conductivities of Si nanowires with various roughnesses

Molecular dynamics (MD) simulations were employed to study the heat transfer in a single crystalline Si nanowire with length smaller than phonon mean free path. Thermal conductivity was calculated using a non-equilibrium method that formed a temperature gradient. The effect of varying roughness sizes and direction on the thermal conductivity at room temperature was studied. It was found that the thermal conductivities were reduced as the size of the roughness increased. Furthermore, variations of the thermal conductivities were more prominent with the perpendicular axis roughness than with the parallel axis roughness. The maximum variation was approximately 63% between smooth and rough models with the same wire size. In addition, the mixed size roughness did not reduce thermal conductivity.