Berlin 2008 – scientific programme
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O: Fachverband Oberflächenphysik
O 74: Metal Substrates: Adsorption of O and/or H
O 74.2: Talk
Thursday, February 28, 2008, 15:15–15:30, MA 141
Oxidation of Fe3Al followed by surface X-ray diffraction — •Claus Ellinger, Vedran Vonk, Navid Khorshidi, Andreas Stierle, and Helmut Dosch — Max-Planck-Institut für Metallforschung,
The interaction between oxygen and alloy surfaces plays a key role in many processes, such as thin film growth, corrosion and catalysis. Due to preferential surface segregation in binary alloys, one of the constituents will react with oxygen to form a thin oxide layer. These oxide layers are used as templates for model catalysts, tunneling barriers in electronic devices, or corrosion-resistant devices. To study the structural composition of the alloy surfaces at realistic conditions and to follow their oxidation process, surface sensitive x-ray diffraction (SXRD) provides a non-destructive in-situ technique. In this talk, the oxidation of Fe3Al(110) will be discussed and compared to NiAl(110). Using AES, LEED and SXRD, we find a chemically well ordered surface of a clean Fe3Al crystal. After exposure to a small amount of oxygen this ordering of the substrate completely disappears in the near surface region and a smooth thin Al2O3 layer is formed. While the fundamental, disordered A2 phase of Fe3Al still exists in the surface region after the oxidation, the two ordered phases of the alloy are only found in the bulk. We therefore conclude that the substrate-oxide interface is still sharp and well-defined, while there is an oxygen induced shift of the stoichiometry within the surface towards the A2 phase.