Regensburg 2010 – scientific programme

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O: Fachverband Oberflächenphysik

O 77: Oxides and insulators: Epitaxy and growth

O 77.5: Talk

Thursday, March 25, 2010, 16:00–16:15, H42

Substrate-induced structural modulation of a CoO(111) bilayer on Ir(100) — •Lutz Hammer, Christina Ebensperger, Wolfgang Meyer, Matthias Gubo, and Klaus Heinz — Lehrstuhl für Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstr. 7, 91058 Erlangen

Oxidation of a monolayer of cobalt deposited on the unreconstructed Ir(100) surface leads to the formation of a CoO(111) bilayer [1]. Quantitative LEED and STM reveal a cobalt layer next to the substrate covered by an oxygen layer. Both layers' hexagonal atomic arrangements are, however, strongly distorted by the quadratic substrate and form a c(10x2) superstructure. The Co layer's buckling characteristics and atomic bond lengths to Ir atoms are consistent with the hard sphere radius of metallic Co. The binding of the oxide to the substrate appears to be characterized by two types of oxygen ions. One type is close to the expected rocksalt-type stacking with respect to the cobalt layer whilst the other type oxygen ions reside nearly on top of Ir atoms with a very short bond length. They are practically coplanar with the Co layer and so almost form a boron-nitride-type oxide. The bond to Ir can be interpreted as a local pinning of the oxide to the substrate, so modulating the entire oxide bilayer.

[1] C. Giovanardi et al., Phys. Rev. B 74 (2006) 125429