THE ROLE OF INTERFACE DISORDER IN THE THERMAL-BOUNDARY CONDUCTIVITY BETWEEN 2 CRYSTALS

The Kapitza conductivity (thermal boundary conductivity (TBC) between two crystals is studied within a simple three-dimensional lattice dynamical model and the role of interface roughness on an atomic scale is investigated. The interface roughness is modelled by a random alloy monolayer A1-xB(x) between the two semi-infinite crystals A and B and is treated by bulk alloy techniques adopted to the interface geometry. The dependence of the TBC on the acoustic mismatch between the two crystals and the degree of roughness is shown for a variety of parameter values. Our results indicate in all cases an increase in the TBC with respect to the planar boundary; the increase becomes quite substantial (about 300%) for large acoustic mismatch values (about 1/5) and is due to diffuse phonon scattering. A comparison with two limiting models that assume only specular or completely diffuse scattering is made.