Berlin 2018 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 9: Focus Session: Frontiers in Reducible Oxide Surface Science I
O 9.4: Vortrag
Montag, 12. März 2018, 12:00–12:15, HFT-FT 131
Progressive reduction from CeO2 to Ce2O3 — •Reinhard Olbrich1, Gustavo E. Murgida2,3, Valeria Ferrari2,3, Clemens Barth4, Ana M. Llois2,3, Michael Reichling1, and M. Veronica Ganduglia-Pirovano5 — 1Fachbereich Physik, Universität Osnabrück, Barbarastr. 7, 49076 Osnabrück, Germany — 2Departamento de Física de la Materia Condensada, GIyA, CAC-CNEA, 1650 San Martín, Buenos Aires, Argentina — 3Consejo Nacional de Investigaciones Científicas y Técnicas - CONICET, C1033AAJ, Buenos Aires, Argentina — 4Aix-Marseille University, CNRS, CINaM UMR 7325, 13288 Marseille, France — 5Instituto de Catálisis y Petroleoquímica, Consejo Superior de Investigaciones Científicas- CSIC, 28049 Madrid, Spain
The progressive reduction from CeO2 to Ce2O3 of a 180nm thick ceria film annealed in an ultra-high vacuum (UHV) environment at temperatures up to 1100 K is observed by direct imaging with a non-contact atomic force microscope (NC-AFM). By combining high-resolution NC-AFM imaging with spin-polarized DFT+U calculations, we identify four surface reconstructions namely √(7)×√(7)R19.1∘ Ce7O12, √(7)×3R19.1∘ Ce3O5, √(3)×√(3)R30∘ Ce3O5 and 1×1 Ce2O3. We combine DFT total energy calculations with statistical thermodynamics to explain the sequence of occurrence of the observed phases and their coexisting at evaluated temperatures. The √(7)×3 phase is the only phase that has an unexpected oblique rather than a hexagonal structure. This phase only exists as a thin reduced over layer and can not be prepared in the bulk.