Local Bonding Analysis of the Valence and Conduction Band Features of TiO2

摘要

An analysis of the valence and conduction band electronic structure of TiO2 as studied by ultraviolet photoemission spectroscopy UPS and x-ray absorption spectroscopy XAS using synchrotron radiation is reported. Valence band spectra from UPS have been deconvolved using a five-peak model. The spectra are interpreted based on the peak assignments to the XAS data and the symmetries of the valence band states. The interpretation is consistent with theoretical calculations of molecular orbitals found in the literature. The removal of the d-state degeneracies that arise from a collective Jahn-Teller splitting of the crystal field split t2g and eg states is observed and scales with the conduction band results from the absorption data. These Jahn-Teller derived energy separations are present in the O K1 and Ti L3 spectra but are not resolved in the photoemission valence band spectra. Two defect states are clearly observed 0.7 and 2.0 eV above the valence band edge and are attributed to the presence of oxygen atom vacancies that are described in terms of Ti3+ states.