PHOTOLUMINESCENCE IN TIO2 ANATASE SINGLE-CRYSTALS

Band gap excitation of pure and Al-doped TiO2 anatase crystals results in visible broad band luminescence which is interpreted as the emission from the self-trapped excitons localized on TiO6 octahedra. With temperature increasing from liquid helium temperature to room temperature, the photoluminescence spectra of the undoped crystal shift to higher energies, while the spectra of the crystal doped with Al shift to lower energies. The influence of the Al dopant centers is understood as an extrinsic self-trapping effect. The luminescence in TiO2 anatase is found to be essentially different from that in TiO2 rutile because of significant structural differences.