Phonon scattering at a crystal surface from<i>in situ</i>-deposited thin films

Abstract

We have studied diffuse scattering of phonons from in situ-deposited thin films (average thicknesses from 1 \AA{} to 1 \ensuremath{\mu}m) using boundary-limited thermal conductivity measurements of the Si substrate. Our temperature range is 0.05-2 K corresponding to dominant phonon frequencies from 5 to 180 GHz. We show that the scattering occurs within the films themselves, not at the sample-film interface, and give evidence that this scattering is caused by structural irregularities of the thin films. Our findings have a direct bearing on the Kapitza resistance problem.