Application of High-Resolution Shadow Casting to the Study of Nucleation and Growth of Gold on Sodium Chloride

Abstract

The method of tantalum–tungsten shadowing has been applied to investigate the initial stages of nucleation and growth of evaporated gold films on sodium chloride cleavage planes. Gold has been evaporated at a fixed evaporation rate at substrate temperatures ranging from 80 to 625 K and the surface plus evaporated layer were shadowed immediately with Ta/W. This treatment helps to prevent artifacts but also enables to distinguish easily between ordered and disordered parts of the NaCl substrate. It was found that the observed density of particles at “saturation” (Ns) is proportional to (exp a/T), where the constant a has two different values for the temperature ranges below and above about 298 K. Several possible interpretations of the occurrence of two activation energies are discussed.