Roughness dependence of phonon-interface thermal transport: Theoretical model and Monte Carlo simulation

Recently, researchers have shown that nanostructured interfaces can manipulate the thermal boundary conductance at the interface, but their conclusions are contradictory, and mechanisms are unclear. In this paper, we investigate the impact of nanostructured interfaces on thermal boundary conductance by considering roughness dependence. To achieve this goal, first, an interface model accounting for spectral specularity and spectral specular and spectral diffuse scatterings is deduced. Next, the Monte Carlo framework of interface treatment for spectral specularity and spectral specular and spectral diffuse scatterings at heterogeneous interfaces is constructed. Then they are validated through comparisons with the discrete-ordinates method and experiments. Finally, the roughness dependence for thermal transport through planar and nanostructured interfaces is studied. Results give a nonmonotonic relationship between thermal boundary conductance and roughness for planar interface, and the manipulation of thermal boundary conductance by nanostructured interfaces depends on the system and interface geometries and the interface roughness. The effect of interface roughness is found to be the dominant impact factor in films with a thickness of tens of nanometers. Further investigations for these small-scale films show that the roughness of their horizontal and vertical interfaces impact thermal boundary conductance differently. Thus, the nonuniform roughness for horizontal and vertical interfaces is proposed to successfully expand the manipulation of thermal boundary conductance in films with small size.