KAPITZA TRANSMISSION THROUGH ATOMICALLY CLEAN SILICON (111) SURFACES

The phonon transmission from atomic clean Si(111) surfaces into liquid helium was studied by the phonon pulse technique. Reflection experime nts and angular resolving transmission experiments were performed to m easure the absolute value of the transmission coefficient and its depe ndence on the phonon emission angle into the solid. A coefficient of t he order of 1% was obtained by a chemical preparation method. We found that the observed anomalous transmission is caused by mass defects. L ocal inhomogeneities caused by the deposition of water molecules on th e surface could be visualised by an enhanced transmission.