Facilitating thermal transport across Si/Ge interface via mass-graded interlayer: The role of elastic and inelastic phonon processes

Abstract

Poor heat dissipation has become the bottleneck that limits the further development of electronics, which lies in the enhancement of interface thermal conductance (ITC). In this paper, the ITC and spectral characteristics of Si/Ge interfaces with mass-graded interlayers are studied through non-equilibrium molecular dynamics simulation. For Si/Ge interface with exponentially mass-graded interlayer, the ITC is 1.73 times larger than that of pure case. More interestingly, the ITC shows a non-monotonic dependence on the number of layers and a double scale behavior when the thickness of each layer increases. To clarify the underlying physical mechanism, spectral phonon transmission function is calculated, and ITC contributed by elastic and inelastic processes is quantified through the Landauer formula. It is revealed that the elastic ITC and inelastic ITC show quite different behaviors with each other when changing the thickness of each layer and number of layers, which is responsible for the abnormal results. The findings here emphasize the mutual control of elastic and inelastic phonon processes at interfaces.