Resonant Photoemission and X-ray Absorption Study of the Electronic Structure of the TiO2−Al2O3 Interface

The electronic structure of the TiO2−Al2O3 interface has been investigated using X-ray absorption and resonant photoemission spectroscopies. These two characterization techniques give a complete picture of the electronic structure of the interface. TiO2 deposits have been grown by thermal evaporation of Ti in an oxygen atmosphere at room temperature. The experimental absorption and photoemission spectra have been measured as a function of the deposition time. In particular, the spectra of a submonolayer of TiO2 grown on the Al2O3 substrate allowed us to study the electronic structure at the interface. The Ti 2p absorption spectra for the TiO2 submonolayer show a significant decrease of the crystal field for the Ti atoms at the interface, which is attributed to a reduction in the covalence of the bonding of the TiO2 overlayer. On the other hand, the corresponding resonant photoemission spectra through the 2p→3d absorption edge show resonance only from Ti states which are distributed at the lower binding en...