Regensburg 2010 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 27: Metal subtrates: Adsorption of O and/or H
O 27.6: Vortrag
Dienstag, 23. März 2010, 11:45–12:00, H42
Growth and morphology of ultrathin TiOx films on Pt3Ti(111) — •Marco Moors1, Séverine Le Moal2,3, Jan Markus Essen1, Conrad Becker2, and Klaus Wandelt1 — 1Institut für phys. und theoret. Chemie, Universität Bonn — 2Centre Interdisciplinaire de Nanoscience de Marseille — 3Technische Universität München
The morphology as well as the surface composition of ultrathin titanium oxide films grown on a Pt3Ti(111) single crystal surface have been investigated as a function of oxidation temperature (700 K to 1000 K) and oxygen exposure (up to 4500 L) using LEED, HREELS and AES. The oxidation of the alloy surface starts at sample temperatures over 500 K but ordered phases are not formed below 800 K. Depending on the used preparation conditions four different ordered oxide phases with both rectangular and hexagonal symmetry have been observed caused by the competitive influence of the hexagonal symmetry of the substrate and the favoured rectangular oxide symmetry. The found structures show a high degree of surface order. Our studies indicate the preference for a two dimensional oxide growth despite very high oxygen exposures (> 900 L). The thicker films are only metastable in a rather small temperature range between 800 and 900 K. Annealing to higher temperatures results in an immediate surface reduction. A complete oxidation to TiO2 is not possible under UHV conditions (p(O2) up to 10-5 mbar). By comparison with the parameters of known stable bulk oxide surfaces a structure proposal of the found oxide phases can be made.