Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 51: Surface chemical reactions I
O 51.11: Vortrag
Donnerstag, 26. März 2009, 18:45–19:00, SCH A01
PrO2−x/Si(111) – A model system for praseodymium oxide based catalysts — •Andreas Schaefer1, Sebastian Lamberti1, Volkmar Zielasek1, Jens Falta2, Thomas Schröder3, and Marcus Bäumer1 — 1Institut für Angewandte und Physikalische Chemie, D-28359 Universität Bremen — 2Institut für Festkörperphysik, D-28334 Universität Bremen — 3IHP microelectronics, D-15236 Frankfurt (Oder), Germany
Praseodymium (Pr) oxides are promising candidates for applications in catalysis and microelectronics due to their variable valency along with a high oxygen mobility. Thin films of the oxide prepared on a Si(111) surface in an UHV environment provide a simplified two-dimensional model system of the oxide catalyst. Such a model system allows insight into the atomic details of oxygen transport and transfer when exposed to adsorbed molecules. Additionally, details on the defect structure of such oxide films can be obtained, which is a crucial point for applications in microelectronics. The films were prepared by molecular beam epitaxy of hex-Pr2O3 and subsequent ex-situ annealing in oxygen atmosphere to obtain cubic PrO2. Here we report on a study on cleaning, reduction and reoxidation of a PrO2−x (x=0−0.5) starting film to obtain a surface with defined oxidation state and stoichiometry. Annealing experiments with and without gas dosage during heating will be compared as well as H2 and O2 plasma treatment. The surfaces have been studied using x-ray photoelectron spectroscopy and low-energy electron diffraction. First thermal desorption spectra of CO adsorbed on the differently prepared surfaces are presented.