Dresden 2011 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 91: Epitaxy and growth: Oxides and insulators

O 91.9: Vortrag

Donnerstag, 17. März 2011, 19:15–19:30, WIL C307

Electronic structure of the c(10x2) cobalt oxide phase on Ir(100): STM and DFT — •C. Tröppner¹, P. Weinhardt¹, M. Reuschl¹, T. Schmitt¹, F. Mittendorfer², J. Redinger², R. Podloucky³, M. Weinert⁴, L. Hammer¹, and M.A. Schneider¹ — ¹Lst. f. Festkörperphysik, U Erlangen — ²Inst. of Applied Physics, TU Wien — ³Inst. of Physical Chemistry, U Wien — ⁴Dept. of Physics, University of Wisconsin-Milwaukee, Milwaukee, USA

We studied the electronic properties of the c(10x2) cobalt oxide bilayer on Ir(100) by low-temperature STM and STS in ultra-high vacuum and by DFT. The oxide films representing a bilayer of CoO(111) were produced by oxidation of cobalt deposited onto Ir(100)(1×1) at elevated temperatures. The DFT calculations were performed using the VASP package employing standard PBE as well as PBE+U to assess the importance of on-site correlations. A symmetric repeated 5 layer Ir slab setup separated by ≥ 16Å vacuum with a bilayer CoO on each side was used. The STS signal was calculated in the Tersoff-Hamann approximation. DFT reveals that STM mainly images the oxygen atoms. As a consequence the subtle modulation caused by the local interaction between the cobalt oxide bilayer and the Ir surface becomes obvious in STM. We also performed STS dI/dV mapping of the CoO films and identified signatures, which can be attributed to oxygen and cobalt features by comparison to the theoretical data. However, STS dI/dV spectra of the c(10x2) but also of other thin cobalt oxide phases on Ir(100) show "zero-bias anomalies" tentatively assigned to the Kondo effect that is not captured by the present state of the calculations.