Electronic Nature of Step-edge Barriers Against Adatom Descent on Transition-metal Surfaces

Abstract

The activation barriers against adatom migration on terraces and across steps play an essential role in determining the growth morphology of surfaces, interfaces, and thin �lms. By studying a series of adatoms on representative transition metal surfaces through extensive �rst-principles calculations, we establish a clear correlation between the preferred mechanism and activation energy for adatom descent at a step and the relative degree of electronic shell �lling between the adatom and the substrate. We also �nd an approximate linear relation between the adatom hopping barriers at step edges and the adatom-surface bonding strength. These results may serve as simple guiding rules for predicting the precise atomic nature of surface morphologies in heteroepitaxial growth such as nanowires.