Seminars Archive

Ultrathin ordered titanium oxide films on Pt(111) properties and perspectives

Abstract
Ultrathin ordered titanium oxide films on Pt(111) surface have been prepared by reactive evaporation of Ti in oxygen. By varying the Ti dose and by careful optimization of the annealing conditions (i.e. temperature and oxygen pressure), we have isolated seven different long-range ordered phases. The different nanostructures have been characterized by LEED, STM, XPS, PED, HREELS, XAS, and valence band spectroscopy. The experimental analysis show that these wide range of structures can be rationalized in two main groups i.e. three stoichiometric phases with a O-Pt interface and four substoichiometric one-monolayer phases, with Ti at the interface with the substrate. For six of these seven phases a structural model, in agreement with the experimental result and supported by DFT calculation, has been proposed The principal interest of stoichiometric phases is related to their structure that is the same of some TiO2 nanosheets obtained by exfoliation of 3D stacked titanates. These nanosheets shows innovative properties and are presumably the building blocks of titania nanotubes. On the other hand three different substochiometric TiOx phases have been used as templates for growing ordered and monodispersed Au nanocluster arrays. Metal-cluster growth on oxide surfaces is currently a very active field of research, within such a topic, gold on titania represents a subtopic of particular relevance because of the peculiar catalytic properties toward CO oxidation at room temperature. Therefore we are now involved in the characterization of chemical properties of these Au monodispersed nanoclusters by TPD analysis.