Effects of Si/Ge superlattice structure with intermixed interfaces on phonon thermal conductivity

Abstract

By means of the Monte-Carlo/Molecular Dynamics and the non-equilibrium Molecular Dynamics methods we investigate the cross- and in-plane thermal conductivities of the (001)-, (110)- and (111)-oriented Si/Ge films (2 − 20 nm) and bulk superlattices with an intermixing at interfaces in comparison with the corresponding alloy structures at 300 K. For the first time the anomalous conductivity reduction of the in-plane thermal transport with respect to the film thickness has been revealed. This effect can be caused by interplay of three phonon scattering mechanisms: the phonon-alloy scattering mechanism, which is dominant, and competing phonon-phonon and phonon-surface scatterings due to the phonon depletion and the surface phonon localization, respectively.