Experimental Evidence of Superdiffusive Thermal Transport in Si0.4Ge0.6 Thin Films

Superdiffusive thermal transport represents a unique phenomenon in heat conduction, which is characterized by a size (L) dependence of thermal conductivity (kappa) in the form of kappa proportional to L-beta with a constant beta 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 Si0.4Ge0.6 thin films grown by molecular beam epitaxy. The cross-plane thermal conductivity of Si0.4Ge0.6 thin films spanning a thickness range from 20 to 1120 urn was measured in the temperature range 120-320 K via a differential three-omega method. Results show that the thermal conductivity follows a consistent kappa proportional to t(0)(.2)(6) power law with the film thickness (t) at different temperatures, providing direct experimental evidence that alloy-scattering dominated thermal transport in SiGe is superdiffusive.

Automated summary

This study provides direct experimental evidence that superdiffusive thermal transport exists in SiGe alloys, as the thermal conductivity follows a power law relationship with film thickness. This research is significant for understanding the unique phenomenon of heat conduction.