Morphology and defect structure of the CeO2(1 1 1) films grown on Ru(0 0 0 1) as studied by scanning tunneling microscopy |
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Authors: | J.-L. Lu H.-J. Gao H.-J. Freund |
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Affiliation: | a Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany b Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100080, China |
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Abstract: | The morphology of ceria films grown on a Ru(0 0 0 1) substrate was studied by scanning tunneling microscopy in combination with low-energy electron diffraction and Auger electron spectroscopy. The preparation conditions were determined for the growth of nm-thick, well-ordered CeO2(1 1 1) films covering the entire surface. The recipe has been adopted from the one suggested by Mullins et al. [D.R. Mullins, P.V. Radulovic, S.H. Overbury, Surf. Sci. 429 (1999) 186] and modified in that significantly higher oxidation temperatures are required to form atomically flat terraces, up to 500 Å in width, with a low density of the point defects assigned to oxygen vacancies. The terraces often consist of several rotational domains. A circular shape of terraces suggest a large variety of undercoordinated sites at the step edges which preferentially nucleate gold particles deposited onto these films. The results show that reactivity studies over ceria and metal/ceria surfaces should be complemented with STM studies, which provide direct information on the film morphology and surface defects, which are usually considered as active sites for catalysis over ceria. |
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Keywords: | Ceria Thin films Defects Scanning tunneling microscopy |
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