Growth of Face-Centered-Cubic Metals on Sodium Chloride Substrates

Abstract

Films of gold, silver, copper, nickel, palladium, and platinum were prepared by evaporation of the metals in ultrahigh vacuum onto hot, vacuum cleaved, sodium chloride substrates. Nickel, palladium, and platinum films that completely covered the surface were single crystals in the orientation of the substrate. Complete gold, silver, and copper films were polycrystals in which there was a tendency for the (111) metal plane to be parallel to the (001) salt surface. Later, it was found that single crystal foils of gold, silver, and copper were obtained if the salt substrate was exposed to air prior to the deposition of metal upon it. Careful comparison of the growth of gold on clean and on air-contaminated salt surfaces has shown that the effect of air is not to improve the alignment of the initial gold nuclei, but is to increase the number of nuclei generated per unit area. This increase causes nuclei to coalesce earlier in film growth. The stage in film growth at which coalescence occurs influences the orientation changes that accompany coalescence, and thereby influences the orientation of the complete film.