Trap-centre recombination processes by rare earth activators in YAlO3 single crystal host

The trapping-recombination processes occurring in YAlO3 single crystals are investigated by wavelength-resolved thermally stimulated luminescence (TSL) studies from 10 to 300 K after x-ray irradiation at 10 K. Undoped crystals and crystals doped with rare earth ions are studied. The results obtained on undoped, Yb3+ -, Eu3+ -, and Tm3+ -doped samples indicate the existence of seven glow peaks due to intrinsic hole traps. Three of them (at 154, 190, and 232 K) are related to different variants of O centers, as demonstrated by the correspondence between the thermal stabilities of such centers detected by electron paramagnetic resonance and the glow peak temperatures. From the analysis of the TSL emission spectra it is found that rare earth ions, after capturing electrons during irradiation, play the role of recombination centers. The thermal depths and the room-temperature lifetimes of the traps are also evaluated. After doping with rare earth ions which are expected to act as hole traps such as Ce3+, Pr3+, and Tb3+ only one main peak is observed, preceded by a nearly temperature-independent emission which is completely suppressed at temperatures higher than the glow peak temperature. For each particular dopant the peak coincides with one of those observed in the undoped crystal while the TSL spectral emission is characteristic of the rare earth ion dopant. To interpret such results we suggest the existence of defect complexes, involving intrinsic defects coupled to Ce3+, Pr3+, and Tb3+ rare earth ions, in which carriers can be transferred from intrinsic levels to the rare earth ion levels, where the radiative recombination occurs. © 2009 The American Physical Society.