Experimental Evidence of Superdiffusive Thermal Transport in SiGe Thin Films.

Superdiffusive thermal transport represents a unique phenomenon in heat conduction, which is characterized by a size () dependence of thermal conductivity (κ) in the form of κ ∝ with a constant β between 0 and 1. Although superdiffusive thermal transport has been theoretically predicted for SiGe alloys, direct experimental evidence is still lacking. Here, we report on a systematic experimental study of the thickness-dependent thermal conductivity of SiGe thin films grown by molecular beam epitaxy. The cross-plane thermal conductivity of SiGe thin films spanning a thickness range from 20 to 1120 nm was measured in the temperature range 120-320 K via a differential three-omega method. Results show that the thermal conductivity follows a consistent κ ∝ power law with the film thickness () at different temperatures, providing direct experimental evidence that alloy-scattering dominated thermal transport in SiGe is superdiffusive.