Modulated SiC nanowires: Molecular dynamics study of their thermal properties

The thermal conductivity of diameter and polytype modulated SiC nanowires is predicted using nonequilibrium molecular dynamics. For the polytype modulated nanowires, the two main SiC polytypes, zinc blende (3C) and wurtzite (2H) were considered. We show that the thermal conductivity of the diameter modulated nanowires may be even smaller than that of the constant diameter nanowire with the small section. This remarkable reduction in thermal conduction is attributed to a significant thermal boundary resistance displayed by the constriction, as measured by independent molecular-dynamics simulations. The constriction resistance is related to the confinement of low-frequency modes, as shown by vibrational density-of-states calculations. We used Monte Carlo simulations to conclude that the value of the constriction resistance may be explained by the specular reflections of this class of modes on the surface surrounding the constriction.