EFFECT OF EXPOSURE TO AIR ON SILVER AND GOLD FILMS DEPOSITED IN ULTRA-HIGH VACUUM

The influence of air on different growth stages of silver and gold films deposited in ultrahigh vacuum (UHV) on mica cleaved in air or vacuum has been studied with electron microscopy. Thin protective layers were condensed in UHV onto parts of the films and the structure and surface topography of protected and unprotected areas were compared after the films had been exposed to air, O2, N2 or H2O vapour. Gold films were stable at all growth stages and thin gold films (10-20 Å) condensed onto silver films at room temperature were effective as protective layers. Silver films changed on exposure to air. The changes were most marked when films deposited at room temperature on vacuum-cleaved mica consisted of polycrystalline networks. The silver contracted and recrystallization enhanced the growth of (111) epitaxed grains into large sheets. The results indicate that water vapour is the active component in air and that it increases the rate of surface self-diffusion of silver. © 1968.