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O: Oberflächenphysik

O 55: Epitaxie und Oberfl
ächenreaktionen

O 55.8: Vortrag

Mittwoch, 9. März 2005, 12:30–12:45, TU EB107

Dynamics of Surface Defects observed on CeO₂ (111) by Dynamic Force Microscopy — •S. Gritschneder¹, Y. Namai², Y. Iwasawa², and M. Reichling¹ — ¹Fachbereich Physik, Universität Osnabrück, Barbarastraße 7, 49076 Osnabrück, Germany — ²Department of Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan

The (111) surface of CeO₂ in various oxidation states is important for catalytic activity and some of its details relating to surface oxygen atoms have already been studied with dynamic scanning force microscopy. The remarkable catalytic properties of ceriumdioxide are strongly connected to the creation, diffusion and healing of oxygen vacancies and, hence, CeO₂ is used as an oxygen storage device in various technical applications like for instance the three-way-catalyst and the solid oxide fuel cell. We demonstrate that dynamic force microscopy is perfectly suitable to investigate nanoscale and atomic size defects on this insulating oxide surface. Our experiments reveal a rich variety of surface defects in form vacancies and protrusions localized at single, well defined lattice sites as well as extended defect formations involving several surface or sub-surface ions. Many of the defects are very stable, but we can show in series of consecutively recorded images that defects can also appear, disappear and change their morphology. Aiming for a chemical identification of the defects, we exposed slightly reduced CeO_2−x(111) surfaces to molecular oxygen and observed the changes in the apparent surface structure. Already at very low dosages of less than 10 Langmuir, we observe effects that we interpret as healing of oxygen vacancies.