Berlin 2012 – wissenschaftliches Programm
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KR: Fachgruppe Kristallographie
KR 10: Crystallography in Nanoscience
KR 10.4: Vortrag
Donnerstag, 29. März 2012, 10:40–11:00, E 124
Structure - stoichiometry relationship of mixed Ce1−xPrxO2−δ (x = 0-1) oxides on Si(111) — •Marvin Zoellner1, Marcus Bäumer2, Michael Reichling3, Henrik Wilkens3, Joachim Wollschläger3, Peter Zaumseil1, and Thomas Schroeder1 — 1IHP, Im Technologiepark 25, 15236 Frankfurt (Oder), Germany — 2Universität Bremen, IAPC, Leobener Str. NW2, 28359 Bremen — 3Universität Osnabrück, Fachbereich Physik, Barbarastr. 7, 49076 Osnabrück, Germany
Cerium and praseodymium oxide thin films are of interest for model catalytic studies. When grown by molecular beam epitaxy on Si(111), CeO2 exists in the fluorite lattice. Praseodymium prefers the 3+ state as Pr2O3, which has either a cubic bixbyite or hexagonal crystal structure. A mixture of both oxides enables to engineer the properties of the catalyst, due to different redox reactivities and lattice alteration. Before model catalytic studies can be carried out, the correlation between crystal structures and stoichiometries of the mixed Ce1−xPrxO2−δ layers must be clarified. We monitored the growth by reflection high energy electron diffraction. X-ray photoemission spectroscopy was applied to determine the stoichiometry. Laboratory and synchrotron based X-ray diffraction was carried out to investigate the crystal structure. The study revealed that Ce1−xPrxO2−δ keeps the Ce4+ related fluorite lattice for low praseodymium concentrations (x = 0.30). However, the crystal lattice is dominated by the Pr3+ state for medium (x = 0.65) and high (x = 0.75) Pr concentrations so that bixbyite and hexagonal structures are formed, respectively.