The influence of previous substrate heat treatment on the epitaxial growth of silver on mica

Abstract

The growth of silver films prepared by evaporation in ultrahigh vacuum onto mica cleaved in air and previously heat treated at various temperatures T H for 24 h was studied by reflection high energy electron diffraction. It was found that for T H < 250 °C the silver films are well oriented from the initial stages of growth. At higher T H the initial stages are characterized by crystallites with random orientation and with two main orientations (each with double positioning). With increasing thickness, first the randomly oriented crystallites disappear and then those with one of the main orientations; finally a single-crystal film is obtained ( T H < 320 °C. For films with a certain thickness it is found that, the higher T H is, the higher is the fraction of randomly oriented crystallites. The results are explained by the decrease in water vapour concentration on the mica surface as T H is increased, which in turn causes the reduction in the orientation of the initial nuclei as well as in their density.