Luminescence and photo-thermally stimulated defect creation processes in PbWO4:Mo,La,Y (PWO III) crystals.

Photoluminescence, thermally stimulated luminescence and electron spin resonance 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⁺, Y³⁺, and Mo⁶⁺ ions. Photo-thermally stimulated processes of electron and hole centers creation under selective UV irradiation of the crystal in the 3.5-5.0 eV energy range and 85-205 K temperature range are clarified and the optically created electron and hole centers are identified. The electrons in this crystal are found to be mainly trapped at the (MoO₄)²⁻ groups as well as at the (WO₄)^2- groups located close to single La³⁺ and Y³⁺ ions, producing electron (MoO₄)^3-, {(WO₄)^3- - La³⁺} and {(WO₄)^3- - Y³⁺} centers. The holes are mainly trapped at the regular oxygen ions O^2- located close to La³⁺ and Y³⁺ ions associated with lead vacancies, producing the O⁻(I)-type centers, or to single Mo ions, producing the O⁻(II) centers. No evidence of single-vacancy-related centers has been observed. The data obtained indicate a small concentration of single (non-compensated) oxygen ( V_O) and lead ( V_Pb) vacancies as the traps for electrons and holes, respectively, which explains more favorable scintillation characteristics of the PbWO₄:Mo,La,Y crystal as compared with the earlier studied PbWO₄:Mo, La and PbWO₄:Mo,Y crystals. [ABSTRACT FROM AUTHOR]