Regensburg 2010 – scientific programme
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O: Fachverband Oberflächenphysik
O 77: Oxides and insulators: Epitaxy and growth
O 77.8: Talk
Thursday, March 25, 2010, 16:45–17:00, H42
From chemisorbed oxygen to ultrathin cobalt-oxides on Ir(100)-(1x1) — •Christina Ebensperger, Matthias Gubo, Wolfgang Meyer, Lutz Hammer, and Klaus Heinz — Institut für Festkörperphysik, Friedrich-Alexander-Universität Erlangen-Nürnberg, Staudstr. 7, 91058 Erlangen
A single monolayer (ML) of cobalt was deposited on Ir(100)-(1x1) and exposed to oxygen at elevated temperatures. As function of oxygen dosage several ordered phases develop, which were studied by means of STM and quantitative LEED.
At low oxygen coverage of 0.25 ML a (2x2) phase develops with hollow site adsorption of chemisorbed oxygen as observed also for other fcc(100) surfaces (R-factor: R = 0.12). With further exposure to oxygen this phase transforms into two different (3x3) phases, (3x3)I and (3x3)II, which can be instantaneously monitored by the LEED intensities. The (3x3)I structure is a periodic arrangement of isolated suboxide rings with Co8O4 stoichiometry (R-factor: R = 0.14), while in the second phase these rings are interconnected by additional oxygen ions (R-factor: R = 0.16). The latter attract the surrounding cobalt ions and reduce their bonding to the substrate. The stoichiometry thereby changes towards Co8O5. With even further exposure to oxygen a c(10x2) phase develops which can be regarded as a heavily distorted bilayer of bulk CoO.