ANNEALING BEHAVIOR OF QUENCH-CONDENSED HYDROGEN AND DEUTERIUM FILMS

We have studied the annealing behavior of thin molecular hydrogen and deuterium films (typical thickness 10 nm) prepared by quench-condensation at 1.5 K on a silver substrate. Changes in the optical thickness and the heterogeneity of the films were monitored using optically excited surface plasmons. Upon annealing the films exhibit an irreversible change from a homogeneous to a strongly heterogeneous structure on a length scale of some hundred nm, accompanied by an apparent loss in optical thickness. This behavior is interpreted as being due to the formation of large bulk crystallites on the surface, resulting from the incomplete wetting of solid hydrogen on silver.