A theory of orientation effects in nucleation on a crystalline substrate

When atoms are deposited from a vapour on to a substrate the growth of the deposit is affected by the nature of the small clusters of atoms formed initially. The possibility is considered that clusters of a given size may be able to adopt more than one shape or orientation and the implications of this for nucleation rates and processes are considered, using an exact treatment of an atomistic model. It is found that several physically distinct mechanisms exist whereby changes in the supersaturation of the incident vapour can affect the proportion of clusters in different orientations; any of these mechanisms can account for the experimental results obtained when gold is deposited on sodium chloride.