Influence of the initial step density on the growth mechanisms of the Fe/Cu( [formula omitted]) interface

Abstract

We report on a scanning tunnelling microscopy study of the Fe/Cu(1 0 0) interface formation at room temperature (RT). From detailed studies of Fe film morphology for coverages<4 ML, we show the influence of the morphology of the initial surface on the growth mechanisms. Under iron deposition a step edge erosion occurs and intensifies with coverage leading to an unexpected flux of Cu atoms from step edges to the growing islands on the terraces. Two-dimensional heterogeneous Cu–Fe islands are formed on the surface with large amount of Cu at least for the two first atomic layers. In the case of a Cu(1 0 0) substrate with a high density of steps, the resulting growth mode is more complex than the layer by layer or bilayer ones, usually proposed in the literature. The excess of Cu atoms in the first growing planes allows a copper segregation at RT for thickness up to 4 ML. The tensile stress in the Cu surface plane, induced by initial iron inclusions, can be responsible for such a behaviour.