Photoluminescence dynamics in strontium titanate

The recombination dynamics of electron-hole pairs of pure and n-doped strontium titanate (STO) bulk samples after an intense UV laser-pulse excitation has been investigated by collecting and analyzing the frequency- and time-resolved photoluminescence (PL) signal, as a function of the sample temperature The observed PL decay is ill the nanosecond time-scale and it shows a peculiar mixed kinetics In particular, two decay channels are clearly singled-out the faster one has a decay-time that is markedly dependent on the photo-excited carrier density and it is well described as a bimolecular recombination process, while the second slower channel shows an excitation-independent rate and follows all unimolecular law. The PL spectra show a considerable variation with temperature, with a previously unreported, pronounced difference between pure and doped samples emerging at high temperatures A first discussion of the possible underlying mechanisms is attempted. (C) 2009 Elsevier B.V. All rights reserved.