OXIDATION OF EPITAXIAL FE FILMS MONITORED BY X-RAY REFLECTIVITY

We have studied the oxidation of thin epitaxial Fe(100) films on MgO(1 00) with and without an Au(100) protecting cap by x-ray reflectivity m easurements. The oxidation was carried out under atmospheric condition s between 20-degrees-C and 200-degrees-C. The results are compared to the oxidation of Fe(110) oriented films on Al2O3(1120BAR) substrates w ith an Au(111) cap. Auger electron spectroscopy before and after oxida tion was carried out for sublimentary chemical information of the surf ace. For the uncovered Fe films we observe smoothly growing oxide film s at the surface during oxidation at elevated temperatures. As expecte d, the Au(100) cap serves as an effective shield against oxidation, wh ile the Au(111) cap, surprisingly, does not. In the case of Au/Fe/Al2O 3, we find Fe2O3 formation at the surface of the Au layer at 200-degre es-C. The different behavior of Au(100) and Au(111) is discussed in te rms of stacking faults and/or domain structure occurring in the latter case during epitaxial growth.