Oxidation of ultrathin iron layers grown on Cu(111)

Abstract

Oxidation of thin iron layers (<25 Å) grown on a Cu(111) substrate is studied at 300 K by Auger spectroscopy, LEED and RHEED. After a 250 L exposure of oxygen, iron is oxidized into Fe 2O 3 or Fe 3O 4. RHEED and LEED experiments gave evidence for the formation of a plane with hexagonal symmetry. The unit cell parameter of this plane is higher than those observed in (111) close packed oxygen planes of the different bulk iron oxides. If the layer is thin (<3 Å), iron is fully oxidized. For thicker layers, an iron underlayer exists. The thickness of the oxide cannot exceed 10 Å.