Impact of surface roughness temperature dependency on the thermal contact resistance between Si(111) and liquidH4e

The thermal contact resistance at a highly polished single-crystal silicon (111)/liquid helium interface has been directly measured from 0.4 to 2.1 K using a single experimental cell. A thermal analysis is presented using the thermal conductivity of the Si which is simultaneously measured. The effect of phonon scattering by nanoscale surface roughness on the observed thermal resistance is investigated. A feature brought to light in our analysis is that the surface roughness which plays an effective role in phonon scattering is temperature dependent. This explains the temperature dependencies of the thermal contact resistance. Comparisons with other experiments are made.