Regensburg 2004 – scientific programme

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O: Oberflächenphysik

O 14: Postersitzung (Adsorption an Oberflächen, Epitaxie und Wachstum, Organische Dünnschichten, Oxide und Isolatoren, Phasenübergänge, Rastersondentechniken, Struktur und Dynamik reiner Oberflächen)

O 14.33: Poster

Monday, March 8, 2004, 18:00–21:00, Bereich C

Growth and morphology of titanium dioxide on a Re(10-10) surface — •Dirk Rosenthal and Klaus Christmann — FU Berlin, Inst. f. Chemie

Titaniumdioxide films were prepared in UHV by co-adsorption of titanium and oxygen on a Re(10-10) surface. The films were characterized by means of LEED, XPS and LEIS. The oxygen partial pressure and substrate temperature, rather than the titanium flux, are crucial parameters that influence the resulting titaniumdioxide structure. Thin films of a few monolayers prepared at 500K exhibit at least three different LEED structures, one of which indicates an epitaxial phase. Preparation at 700K on the other hand (after formation of several transient LEED phases in the sub- and monolayer regime), leads to a (2x2) structure with missing reflexes in (0, k ± 1/2) positions. The latter are characteristic of a glide mirror plane in [1-210]-direction (parallel to the troughs of the Re-surface). A prerequisite for this behavior is a non-primitive unit mesh. XP-spectra of ultrathin titania films (around 1ML) suggest a stoichiometric structure that could be attributed to TiO₂ . We present a structure model to explain the (2x2) phase.