Enhancing phonon transmission across a Si/Ge interface by atomic roughness: First-principles study with the Green's function method

Abstract

Knowledge on phonon transmittance as a function of phonon frequency and incidence angle at interfaces is vital for multiscale modeling of heat transport in nanostructured materials. Although thermal conductivity reduction in nanostructured materials can usually be described by phonon scattering due to interface roughness, we show how a Green's function method in conjunction with the Landauer formalism suggests that interface roughness induced by atomic mixing can increase phonon transmission and interfacial thermal conductance. This is an attempt to incorporate first-principles force constants derived from ab initio density-functional theory (DFT) into Green's function calculation for infinitely large three-dimensional crystal structure. We also demonstrate the importance of accurate force constants by comparing the phonon transmission and thermal conductance using force constants obtained from semiempirical Stillinger-Weber potential and first-principles DFT calculations.