Effect of interface density, quality and period on the lattice thermal conductivity of nanocomposite materials

Abstract

We examine the effects of interface density, quality, and period size on the lattice thermal conductivity of nanocomposite materials within the framework of a recently developed extended modified effective medium approach. A density functional theory and Boltzmann equation based semi-ab initio approach is used to calculate the constituent thermal conductivities, and the effective thermal boundary conductance is computed by modeling interface roughness based on a realistic combination of acoustic mismatch and diffuse mismatch contributions, for systems with anisotropic (directionally dependent) and isotropic thermal conductivities. Results obtained for Si/Ge and MoS2/WS2 systems indicate that the effective cross-planar thermal conductivity of planar superlattice systems is closely related to the thermal boundary resistance of the system for small superlattice periods, whereas in nanodot superlattices, the effective thermal conductivity for small particles is primarily regulated through the effective scattering lengths used in the calculation of the insert and matrix conductivities.