Radiation annealing of epitaxial silver films

Epitaxial silver films grown by vapour deposition on mica in a vacuum of 10-4 Pa have low temperature resistivities which are dominated by size effects. Careful production techniques at 3500C has led to thin films (400 nm) with resistivity ratios (room temperature resistance divided by resistance at 4.2 K) of greater than one hundred. These values are higher than those obtained in previous studies and indicate the quality of the films. It was found from reflection high energy electron diffraction evidence that the films have a <111> axis normal to the substrate while electron micrographs show large grains of order 1 μm. Surprisingly, if these films, after cooling to room temperature, are annealed by radiation from a tungsten filament their resistivity ratios are increased by an order of 10-20%. This indicates a substantial recrystallization and enhancement of grain size-the surface scattering in these films being exposed to air before measurement is assumed unchanged. Why such a radiation anneal for only a few seconds should be so significant by comparison to a thermal anneal at 3500C is unclear. Results are also presented on samples produced on mica substrates held at room temperature. In this case films produced during exposure to the radiation from the tungsten filament have a large, factor of 2, enhancement in the resistivity ratio which is clearly attributable to recrystallization. (author)