Structure of epitaxial iron oxide films grown on Pt(100) determined by low energy electron diffraction

Ordered iron oxide films from submonolayer to multilayer thickness were grown layer-by-layer onto a Pt(100) substrate by iron deposition and subsequent oxidation at 900 K and 10− 6 mbar oxygen. Their structure and composition were determined by low energy electron diffraction (LEED) and Auger electron spectroscopy (AES). The hexagonal reconstruction of the clean Pt(100) surface is lifted underneath the iron oxide film. The first monolayer forms a c(2 × 10) coincidence structure with respect to an unreconstructed Pt(100) surface. For this monolayer the best fit structure, as provided by a LEED intensity analysis, consists of a slightly distorted hexagonal close-packed iron-oxygen bilayer with oxygen on top. The average platinum-iron and iron-oxygen interlayer distances are 1.61 and 1.26 Å, respectively. The iron and oxygen planes are buckled by 0.5 and 0.3 Å, respectively. Thicker films grow in (111) orientation of Fe3O4 and form the same surface structure as Fe3O4 multilayer films grown on Pt(111).