Epitaxy of Iron on Various Ruthenium Surfaces: Occurence of a New Fe Phase

Abstract

We have deposited Fe on (0001) and (11$\overline{2}$2) Ru surfaces. The RHEED patterns of Fe layers on these two different surfaces show perfect 2 dimensionnal epitaxy. The symmetry of the RHEED patterns is clearly 6 fold in the case of the (0001) growth direction. The RHEED patterns in the case of Fe deposited on (11$\overline{2}$2) surface are the same as those obtained from the clean Ru surface. The structure of the Fe surface is then exactly pseudomorphous to the Ru surface in both cases. Superlattices of these new Fe atomic layers with Ru have been achieved. We have deduced from X-ray diffraction, the average interplanar spacing $\overline{d}$ and we have demonstrated the hexagonal close packed stacking sequence of the entire superlattice. Plots of $\overline{d}$ versus the average atomic composition are used to determine the value of Fe interplanar spacing as 2.075Šand 1.08Šfor the (0001) and the (1122) plane respectively. We are then able to determine the average Fe atomic volume, 12.8ų. We propose that Fe is in an expanded new metastable hexagonal phase.