AVS 49th International Symposium
    Surface Science Tuesday Sessions
       Session SS3-TuA

Paper SS3-TuA8
Vanadium Oxide Nanostructures on Rh(111): Novel Oxide Phases at the Interface@footnote 1@

Tuesday, November 5, 2002, 4:20 pm, Room C-112C

Session: Metal/Oxide Surfaces
Presenter: F.P. Netzer, Karl-Franzens University Graz, Austria
Authors: J. Schoiswohl, Karl-Franzens University Graz, Austria
S. Surnev, Karl-Franzens University Graz, Austria
S. Eck, Karl-Franzens University Graz, Austria
M.G. Ramsey, Karl-Franzens University Graz, Austria
F.P. Netzer, Karl-Franzens University Graz, Austria
Correspondent: Click to Email
Ultrathin layers of materials develop novel physical and chemical properties due to confinement and interfacial proximity effects, which are not shared by their respective bulk phases. Here we report a study of thin vanadium oxide layers on Rh(111) surfaces using STM, STS, LEED, and XPS with synchrotron radiation. We have fabricated vanadium oxide nanostructures on Rh(111) by reactive evaporation of vanadium metal in an oxygen atmosphere onto the heated substrate surface and have characterised the atomic structures of the V-oxide with STM (STS) and LEED; the oxidation state of the oxide layers have been followed by XPS. We find a complex phase diagram of oxide structures as a function of oxide coverage and temperature, and observe a range of well-ordered two-dimensional oxide phases with novel structural properties. At submonolayer coverages higher oxidation states (@>=@4@super+@) prevail [(@sr@7x@sr@7) and/or (@sr@13x@sr@13) structures], whereas the oxidation state converges to 3@super+@ and a bulk-type V@sub2@O@sub3@ phase forms for thicker layers (> 2-3 ML). The monolayer phase is distinguished by a Moiré-type STM structure, resulting from the lattice mismatch between the ordered oxide overlayer and the substrate. Reduced oxide phases are obtained after vacuum annealing treatments, displaying a fascinating structural complexity, with e.g. (5x5), (5x3@sr@3), (9x9) and other structures. @FootnoteText@ @footnote 1@Supported by the Austrian Science Foundation.