PLANE-SPECIFIC OXIDE STOICHIOMETRIES ON FE SINGLE-CRYSTAL SURFACES

A high-energy ion scattering study reveals that oxide layers on Fe(100 ) and Fe(110) have different average stoichiometries if the oxides are grown at room temperature. On Fe(110), Fe2O3 is observed, in contrast with Fe(100) where Fe0.95O has been observed. This difference persist s if the surfaces are precovered with one monolayer platinum. On the b asis of the stoichiometries the geometrical thicknesses at which the o xidation process saturates at room temperature is found to be equal fo r both surfaces, despite the larger oxygen uptake by the Fe(110) surfa ce in saturation. Equal thicknesses are in agreement with the Fromhold -Cook theory of metal oxidation.