Regensburg 2007 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 44: Poster Session II (Semiconductors; Oxides and Insulators: Adsorption, Clean Surfaces, Epitaxy and Growth; Surface Chemical Reactions and Heterogeneous Catalysis; Surface or Interface Magnetism; Solid-Liquid Interfaces; Organic, Polymeric, Biomolecular Films; Particles and Clusters; Methods: Atomic and Electronic Structure; Time-resolved Spectroscopies)

O 44.64: Poster

Mittwoch, 28. März 2007, 17:00–19:30, Poster C

Cerium oxide films on TiO_x coated Pt(111)-single crystals — •Thorsten Staudt and Klaus Schierbaum — : Institut für Experimentelle Physik der kondensierten Materie, Abteilung für Materialwissenschaft, HHU Düsseldorf, 40225 Düsseldorf

The epitaxial growth of thin and continuous CeO₂(111) films on metal surfaces suffers from the preferential formation of a 3 D-like morphology, even though epitaxial relationships exist with the substrate lattices. This holds for films prepared by reactive evaporation of Ce in O₂ on Pd(111) and Rh(111)[1], or by oxidation of an ordered surface alloy Pt₅Ce/Pt(111)[2]. One may expect a decreased lattice mismatch if metal surfaces are used that are coated with ultra thin and ordered oxide-based buffer layers. As a candidate we have chosen the ”wagon wheel” phase of TiO_x grown on a Pt(111) surface which reveal a hexagonal symmetry and an interatomic spacing of 3.26 Å. This value is closed to the lattice constant of 3.86 Å for CeO₂(111).[3] The film is 1.2 ML thick and shows a continuous morphology in STM.

CeO_x films are subsequently grown by thermal evaporation of cerium in O₂ at RT. The films were analysed by LEED and XPS to determine the geometric structure, chemical composition and stoichiometry. First measurements reveal a change in the stoichiometry of the TiO_x film that is discussed in terms of an interface reaction. Additional information on the initial stages of growth is obtained from STM.

[1]: S. Eck et al., Surf. Sc. 520 (2002), 173-185 and reference therein

[2]: U. Berner and K. Schierbaum, Phys. Rev. B 65 (2002), 235404

[3]: F. Sedona et al., J. Phys. Chem. B 109 (2005), 24411-24426