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

Abstract

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 3.5–5.0eV energy range and the 85–205K 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.