Luminescence and photothermally stimulated defects creation processes in PbWO4:La3+, Y3+ (PWO II) crystals

Photoluminescence and thermally stimulated luminescence (TSL) are studied for a PbWO4 crystal grown by the Czochralski method at Bogoroditsk Technical Chemical Plant, Russia from the melt with a precise tuning of the stoichiometry and co-doped with La3+ and Y3+ ions (the PWO II crystal). Photothermally stimulated processes of electron and hole centers creation under selective UV irradiation of this crystal in the 3.5-5.0 eV energy range and the 85-205 K temperature range are clarified and the optically created electron and hole centers are identified. The electrons in PWO II are mainly trapped at the (WO4)2− groups located close to single La3+ and Y3+ ions, producing the electron {(WO4)3−-La3+} and {(WO4)3−-Y3+} centers. The holes are mainly trapped at the regular oxygen ions O2− located close to La3+ and Y3+ ions associated with lead vacancies, producing the hole O−(I)-type centers. No evidence of single-vacancy-related centers has been observed in PWO II. The data obtained indicate that excellent scintillation characteristics of the PWO II crystal can be explained by a negligible concentration of single (non-compensated) oxygen and lead vacancies as the traps for electrons and holes, respectively.