A UV-induced one-dimensional motion of titanium ions in perovskite titanates

Abstract

The UV irradiation effect in the practical luminescence material (Pr, Al)-doped SrTiO3 was investigated by x-ray absorption spectroscopy at the Ti K-edge. Two characteristic peaks observed in difference spectra between UV off- and on-spectra show different UV energy dependence; above the common onset UV energy of ∼3.3 eV, which is nearly equal to the band-gap energy, a difference peak at the main absorption edge changes its intensity in accordance with the photoluminescence excitation spectrum, while another difference peak in the pre-edge region does not. Through the consideration of the energy scheme, the Ti 3d conduction-band bottom is responsible for the pre-edge features and is rather insensitive to UV energy, whereas the main edge together with other features in the higher-energy region is attributable to the upper-lying 4p states that are strongly influenced by UV light via valence holes. These results enable us to propose a mechanism of UV absorption followed by visible light emission. © 2009 IOP Publishing Ltd.