Nanoscale Surface Roughness Contribution to the Kapitza Resistance Between Superfluid He and Silicon

Measurements of the Kapitza resistance have been made on single Si(001) crystals at T > 1.5 K. The surface morphology of the samples was characterised by Atomic Force Microscopy (AFM). The results, interpreted using the Adamenko and Fuks (AF) model, demonstrate that nanometre-scale roughness produces diffuse and/or resonant phonon scattering. This explains the discrepancy between the measured Kapitza resistance and the Khalatnikov values.