Correlation between Defect and Lattice States on Modulated TiO2(110) during Redox Reaction

The correlations between the oxidation states and the ultrahigh vacuum-reconstructed TiO2(110) surface give insight into TiO2’s defects, such as oxygen vacancy (Vo) and Ti interstitial, which induce excess electrons into the surface. Here, the nature of the atomic defects of TiO2(110) was investigated by combining scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) during redox reactions. We observed the reduced TiO2(110) by STM measurements, which was exposed to O2(g) and annealed to modulate the surface. The inverse changes were exhibited in the defect-related XPS peaks, Ti3+ in Ti 2p and the defects in O 1s, compared to the lattice-related peaks, Ti4+ in Ti 2p and O2– in O 1s, because of Vo healing and formation. XPS results show that the additional O2(g) dosing onto the oxygen-fully covered TiO2(110) induced the TiOx island formation, emphasizing the integrated analysis of the TiO2(110) surface reconstruction observation and the core-level spectral information.