Tunable persistent photoresponse in reduced PMN-PT crystals

By means of a thermal annealing in oxygen deficient atmosphere we have been able to trigger persistent photoconductivity (PPC) at UV in commercial PMN-PT crystals. We have explored the time dependent response of PC at different annealing times observing a decrease of PC as the annealing time increases. At low UV intensities, the time dependent PC curves can be well fitted using a model that reflects a competition between the photogeneration of carriers and the recombination at recombination centers. At high UV intensities we have observed an overshoot of PC during the illumination stage and negative PC values after illumination is removed. These results can be explained adding an extra term to the previous model that accounts a dominant contribution of radiative (band to band) recombination although the presence of deep traps also plays a crucial role. Surface effects originated by band bending also influence the time dependent PC.