Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 3: Oxides and insulators I
O 3.4: Vortrag
Montag, 23. März 2009, 12:00–12:15, SCH A01
Ultrathin titanium oxide films grown on Pt3Ti(111): Electronic and structural characterization — •Séverine Le Moal, Marco Moors, Conrad Becker, and Klaus Wandelt — Institute of Physical and Theoretical Chemistry, University of Bonn, Wegelerstr. 12, D-53115 Bonn, Germany
As TiO2-supported platinum is a well-known catalyst, e.g. for CO hydrogenation, the formation of titanium oxides on Ti-Pt alloy surfaces raises much interest. In this work the electronic and structural properties of ultrathin titanium oxide films grown on a Pt3Ti(111) single crystal have been investigated by ultraviolet photoelectron spectroscopy (UPS) and low energy electron diffraction (LEED) as a function of oxygen pressure (10−8 to 10−5 mbar), oxygen exposure (up to 9000 L) and oxidation temperature (300 to 1000 K). For low oxygen exposures (below ∼ 200 L) and above 800 K, a quasi-hexagonal structure (a = 3.35 Å, b = 3.25 Å, α = 124∘) with two domains rotated by 8∘ with respect to each other prevails. Upon oxidation at higher exposures and above 900 K a hexagonal structure (a = 3.20 Å) with two domains rotated by 8∘ with respect to each other is predominantly observed. In this case the p(2×2) structure attributed to the Pt3Ti(111) substrate is no longer present, indicating a possible segregation of titanium to the subsurface. Despite the variety of ordered structures, which have been found for different oxidation conditions, no significant differences in the shape of the valence band spectra have been observed.