Regensburg 2010 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

O: Fachverband Oberflächenphysik

O 41: Poster Session I (Semiconductor Substrates: Epitaxy and growth; Semiconductor Substrates: Adsorbtion; Semiconductor Substrates: Solid-liquid interfaces; Semiconductor Substrates: Clean surfaces; Oxides and insulators: Epitaxy and growth; Oxides and insulators: Adsorption; Oxides and insulators: Clean surfaces; Organic, polymeric and biomolecular films - also with adsorbates; Organic electronics and photovoltaics, Surface chemical reactions; Heterogeneous catalysis; Phase transitions; Particles and clusters; Surface dynamics; Surface or interface magnetism; Electron and spin dynamics; Spin-Orbit Interaction at Surfaces; Electronic structure; Nanotribology; Solid/liquid interfaces; Graphene; Others)

O 41.45: Poster

Dienstag, 23. März 2010, 18:30–21:00, Poster B1

Non-equilibrium structures in Ultrathin V-Oxide films on Rh(111) under Reaction Conditions: The O2 + H2 reaction with and without alkali promotion — •Martin Hesse, Florian Lovis, and Ronald Imbihl — Institut für Physikalische Chemie und Elektrochemie, Leibniz-Universität Hannover, Callinstr. 3-3a, D-30167 Hannover, Germany

As a model system for vanadium-oxide based catalysts we prepared ultrathin vanadium oxide films on a Rh(111) surface1. At 400°C 0.1, 0.25 and 2.4 ML of vanadium were evaporated in oxygen with p(O2)=2*10-7 mbar. After characterization with LEED and Auger electron spectroscopy the films were subjected to the O2 + H2 reaction using photoemission electron microscopy (PEEM) as spatially resolving method. After evaporation a large variety of differently ordered Rh(111)/V/O phases were identified in LEED. The O2 + H2 reaction was studied in the 10-8 - 10-5 mbar range at temperatures between 400 and 500°C. With PEEM we observe that under reaction conditions the film is no longer homogeneous but reaction fronts and stationary Turing-like patterns develop. In the evaporated V-film we find partially ordered patterns which are very stable and change only very slowly after turning off the gases. The patterns induced by the reaction are discussed in the context of the concept of reactive phase separation. When we promote the Rh(111)/V/O-system with alkali metals turbulent spatialtemporal patterns are found.

[1] Surnev, S., M.G. Ramsey, and F.P. Netzer, Progress in Surface Science, 2003. 73, 117.