Initial Stage of Epitaxial Growth of Evaporated Gold Films on Sodium Chloride

The initial stage of the formation of evaporated gold films from 0.5 A to 100 A in mean thickness on cleavage surfaces of sodium chloride was studied by means of a transmission electron microscope. Above the epitaxial temperature, 330°C, gold particles have the so-called parallel orientation. Twin orientations are introduced by coalescence of particles initially formed, with the increase in mean thickness. Below the epitaxial temperature, compound particles are formed at a very early stage of deposition corresponding to the mean thickness of 2 A. With the increase in mean thickness, their structure is modified by coalescence of particles. An essential difference in the size distribution and the crystallographic orientation of gold particles is found between the step-free and step-rich regions of the cleavage surface. Surface migration of gold atoms on the substrate surface is also studied in connection with the difference of amounts of gold between the step-free and step-rich regions.