Role of oxygen deposition pressure in the formation of Ti3+ defect states in TiO2 (001) anatase thin films

We report the study of anatase TiO2 (001)-oriented thin films grown by pulsed laser deposition on LaAlO3 (001). A combination of in situ and ex situ methods have been used to address both the origin of the Ti3+ localized states and their relationship with structural and electronic properties at surface and subsurface. Localized in-gap state are analyzed by resonant x-ray photoelectron spectroscopy and related to Ti3+ electronic configuration, homogeneously distributed over the entire film thickness. We find that an increase of the oxygen pressure corresponds to an increase of Ti3+ only in a well-defined range of deposition pressure; outside of this range Ti3+ as well as the strength of the in-gap states, are reduced.