Photoluminescence of TiO2: Effect of UV Light and Adsorbed Molecules on Surface Band Structure

The photoluminescence (PL) of TiO2 at 529.5 nm (2.34 eV) has been found to be a sensitive indicator of UV-induced band structure modification. As UV irradiation occurs, the positive surface potential changes and shifts the depth of the depletion layer. In addition, reversible band bending due to the adsorption of the electron-donor NH3 and CO molecules has been observed in measurements combining PL with FTIR surface spectroscopy. It has been found that the O-2 molecule acts in two ways: as a reversibly adsorbed electron-acceptor molecule and as an irreversibly adsorbed molecule that heals natural oxygen vacancy defects in the near-surface region.