Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 27: Poster Session I (Methods: Scanning probe techniques; Methods: Atomic and electronic structure; Methods: Molecular simulations and statistical mechanics; Oxides and Insulators: Clean surfaces; Oxides and Insulators: Adsorption; Oxides and Insulators: Epitaxy and growth; Semiconductor substrates: Clean surfaces; Semiconductor substrates: Epitaxy and growth; Semiconductor substrates: Adsorption; Nano- optics of metallic and semiconducting nanostructures; Electronic structure; Methods: Electronic structure theory; Methods: other (experimental); Methods: other (theory); Solutions on surfaces; Epitaxial Graphene; Surface oder interface magnetism; Phase transitions; Time-resolved spectroscopies)
O 27.49: Poster
Dienstag, 24. März 2009, 18:30–21:00, P2
Vanadium oxide films on W(110) and on natively oxidized Si: flat and nanostructured model catalysts — •Benjamin Borkenhagen1, Jöran Bauchrowitz2, Gerhard Lilienkamp1, and Winfried Daum1 — 1IPPT TU Clausthal — 2MPI Hannover
We present results on structural and chemical properties of VOx films prepared in two different ways: by V evaporation in an UHV system under O2 atmospheres on W(110) and by a sol-gel process on Si substrates covered with a native oxide. Under oxidizing or reducing conditions at elevated temperatures the ultrathin VOx films on W(110) can be transformed into several superstructures, e.g. (3x1), (2x1) or nearly hexagonal superstructures the latter observed in several orientations relative to the substrate as revealed by LEED. By analysis of AES we are able to relate these superstructures to W-V surface alloys, WOx or VOx in various oxidation states. We have derived a preliminary diagram of the existence range of surface phases of VOx on W(110). We investigated the films with Low Energy Electron Microscopy (LEEM) to determine domain sizes and alignment and to see how transformations between different superstructures occur. Ultrathin VOx films with low roughness were prepared by a sol-gel process. Depending on subsequent heating, our AFM studies show the formation of multiple surface topographies such as plateaus, needle-like crystallites and tubs. AES and tunneling AFM (TUNA) were used to determine chemical and physical properties of the structures. LEEM has been applied to distinguish between conducting and insulating crystallites and to study changes in conductivity during annealing of the samples in UHV.