Core and Valence Band Photoemission Spectroscopy of Well-Ordered Ultrathin TiOx Films on Pt(111)

Abstract

Well-ordered ultrathin TiOx layers on Pt(111) surface, prepared by reactive evaporation of Ti in oxygen, were characterized by means of Ti 2p and O 1s core level and by valence band photoelectron spectroscopy. Depending on the details of the preparation procedures, a total of six well-ordered structures, each of them characterized by a well-defined low energy electron diffraction pattern, were obtained. The core level data show that this wide range of structures can be rationalized in two main groups, i.e., a group of three stoichiometric (labeled as k‘, rect, and rect‘) and a group of a three substoichiometric (labeled as z, z‘, and w) ordered films. The valence band data are rather consistent with this basic distinction. In fact, valence band spectra relative to stoichiometric or substoichiometric films share common features and are quite different from spectra relative to the other group. On the other hand, the valence band data appear to be more sensitive to the details of the film structure by also d...