Dresden 2009 – scientific programme

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O: Fachverband Oberflächenphysik

O 3: Oxides and insulators I

O 3.7: Talk

Monday, March 23, 2009, 12:45–13:00, SCH A01

Oxygen-deficient cobalt oxide monolayer on Ir(100)-(1x1) — •Christina Ebensperger, Matthias Gubo, Wolfgang Meyer, Lutz Hammer, and Klaus Heinz — Lehrstuhl für Festkörperphysik, Universität Erlangen-Nürnberg, Staudtstr. 7, 91058 Erlangen

When cobalt of slightly less than a mononolayer deposited on Ir(100)-(1×1) is oxidized under oxygen-deficient conditions a new ultrathin cobalt-oxide is formed. It exhibits a (3×3) superstructure on the substrate which can be transformed reversibly into an oxygen-rich c(10×2) structure as described in ref. [1].

The crystallographic structure of the new oxide was determined by quantitative LEED using an exceptionally large data base of more than 12.000 eV. Excellent agreement between experimental and model intensities was achieved (Pendry R-factor: 0.16). The analysis reveals an extremely oxygen-deficient oxide consisting of eight cobalt and only five oxygen ions per (3×3) unit cell with the oxygen located on top of iridium atoms. Four oxygen ions 3-fold coordinated to cobalt are grouped symmetrically around one oxygen ion which in turn is 4-fold coordinated to cobalt. The cobalt ions are closer to the substrate than the oxygen ions, yet not as much as expected from thin cobalt films on iridium. The iridium atoms with oxygen ions on top are displaced by 0.1 Å into the top Ir layer.

The findings of the LEED analysis are corroborated by STM investigations. Depending on the tunnelling conditions either oxygen or the underlying substrate is imaged.

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