Effect of H2O and NH3 contaminants on the epitaxial growth of silver on sodium chloride

Abstract

The influence of H2O and NH3 contaminants on the epitaxial growth of Ag films on (100) NaCl substrate was studied. The contamination effect on NaCl cleaved in air due to the H2O atmospheric vapours was removed with a prolonged treatment of the NaCl substrate in vacuum at 10−2 Torr. The positive contaminating effects are interpreted, through quite a general model, in terms of the adsorption of the contaminant molecules on the NaCl surface. These adsorbed molecules, in the very early stages of the nucleation, allow the growth of Ag nuclei in the (100) orientation and prevent formation of nuclei in other crystallographic orientations. It is assumed that the interaction between contaminant molecules and ionic crystal substrate occurs mainly through the molecular dipole moment of the contaminating vapour.