Photo-induced defects of metal oxides: MgO and rutile TiO2

Abstract When MgO and rutile TiO 2 are irradiated with ultraviolet laser light ( λ =325 nm, hν =3.81 eV) in vacuum, their photoluminescence spectra change in intensity and/or in spectral structure with increasing irradiation time. By irradiating with the same laser light at room temperature in O 2 gas, their original photoluminescence re-appear. Such reversible phenomena are results of photo-induced oxygen desorption and adsorption at surfaces. The mechanism and dynamics of the observed photo-induced spectral transitions are discussed on the basis of the exciton theory.