EARLY STRUCTURAL STAGES OF METALLIC EPITAXY - THE MODEL CASE OF FE/CU (100)

By epitaxial growth of iron on Cu(100) phases of fcc-Fe can be stabilized at room temperature and below. Dependent on coverage the films show various superstructures which we investigate by quantitative analysis of low-energy electron diffraction intensities. There are three coverage regimes, whereby in the first one (Theta less than or equal to 4 ML) all iron layers are considerably reconstructed and are fcc(100) layers only on average. Upon further iron deposition (5 ML < Theta < 10 ML) subsurface iron layers flatten and only the top layer is reconstructed. Simultaneously, the epitaxial growth seems to change from pseudomorphic to nonpseudomorphic. At about 10 ML there is a 1. order phase transition fcc(100) double right arrow bcc(110), the latter phase being stable at higher coverages. It turns out that the reconstruction of layers always entails an increased atomic volume available for iron atoms involved in the reconstruction. In turn this is consistent with magnetic properties known for the iron films from the literature, i.e., bulk ferromagnetism in the first coverage regime and only surface ferromagnetism in the second. So, magnetic and structural properties are shown to be closely related.