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O: Oberflächenphysik
O 11: Poster (I)
O 11.22: Poster
Monday, March 22, 1999, 19:30–22:30, Aula
Adsorption of O2, CO and C2H2 on ordered Eu - and Sm - films — •Reiner Wahl, Serguei L. Molodtsov, and Clemens Laubschat — Institut f"ur Oberfl"achenphysik und Mikrostrukturphysik, TU Dresden, 01062 Dresden
We report on a photoemission study (PE) of adsorption of oxygen, carbon monoxide and acetylene on ordered thin films of the rare earth metals europium and samarium. The films with thicknesses between 20 Å and 150 Å were grown epitaxially on a W(110)-substrat and characterised by LEED and PE. For europium the existence of a new phase is confirmed, characterized by a hexagonal LEED pattern. For samarium the surface-valence-transition-induced 5 × 5 surface reconstruction was found at room-temperature. At this temperature the adsorption of the used gases may be characterized as dissoziativ chemisorption. In case of O2-adsorption a complete oxidation of the film is achieved leading to coexistence of different oxide phases. In case of CO and C2H2 passivation of the surface is observed. Simple structure-formation models and possible explanations of this behaviour will be discussed.