Characterisation of bandgap states in V-doped TiO2 by high-resolution X-ray photoemission spectroscopy

Core- and valence-level photoemission spectra of V-doped TiO2 have been measured with monochromatic Al-Kα X-ray excitation. UHV annealing of as-presented samples leads to the appearance of a photoemission peak above the O 2p valence band within the bulk bandgap of TiO2. Simultaneous changes in V core-level spectra allow this peak to be identified as arising from electrons trapped on vanadium ions to generate localised VIV centres.