Regensburg 2007 – scientific programme
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O: Fachverband Oberflächenphysik
O 59: Oxides and Insulators: Clean Surfaces
O 59.3: Talk
Thursday, March 29, 2007, 16:15–16:30, H41
Self-Assembled Sub-Surface Oxygen Vacancy Arrays on Reduced CeO2(111) — •Stefan Torbrügge1, Michael Reichling1, Seizo Morita2, and Oscar Custance2 — 1Fachbereich Physik, Universität Osnabrück, Barbarastr. 7, 49076 Osnabrück, Germany — 2Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka, Japan
In this contribution, we present atomic resolution dynamic scanning force microscopy (SFM) measurements of the reduced CeO2(111) surface performed at 80 K. We have been able to clearly recognize surface and sub-surface oxygen vacancies and to corroborate the topographic heights predicted by previous theoretical calculations [1,2]. A detailed structural analysis of these two types of oxygen vacancies, as well as other surface defects, is presented. We found that some terraces of the prepared CeO2(111) surface are dominated by sub-surface oxygen vacancies. By the combined analysis of two complementary SFM signals, namely topography and dissipation, we are able to clearly locate each sub-surface oxygen vacancy. Our findings suggest that sub-surface oxygen vacancies do not cluster together but tend to self-assemble in ordered arrays leading to a (2x2) locally reconstructed surface. Thus, we present experimental evidences that single sub-surface vacancies, ordered in arrays at high concentration, are energetically more favorable than sub-surface vacancy clusters.
[1] F. Esch et al., Science 309, 752 (2005)
[2] S. Fabris et al., J. Phys. Chem. B 109, 22860 (2005)