ESR and TSL study of hole capture in PbWO_4:Mo,La and PbWO_4:Mo,Y scintillator crystals

TL;DR

This study investigates hole trapping and recombination in double-doped PbWO_4 crystals using ESR and TSL, revealing defect-specific hole centers and their thermal stability, advancing understanding of scintillator defect processes.

Contribution

It provides new insights into hole localization, defect types, and thermal stability in PbWO_4:Mo,La and PbWO_4:Mo,Y crystals, using combined ESR and TSL techniques.

Findings

Holes are trapped at lattice oxygen ions near defects.

Different O^- centers exhibit distinct thermal stabilities.

Recombination processes involve specific traps like Pb^+ and (MoO_4)^3-.

Abstract

The processes of hole localization in double-doped PbWO_4:Mo,La and PbWO_4:Mo,Y single crystals have been studied by continuous wave and pulse electron spin resonance (ESR) and thermally stimulated luminescence (TSL) methods. We show that the holes created by the UV irradiation are preferably trapped at lattice oxygen ions in the vicinity of perturbing defects such as lead vacancies, impurity ions (La, Y, Mo), and other lattice imperfections. This leads to a variety of O^- centers, which differ both by thermal stability (from about 170 K up to 240 K) and ESR parameters. The hole centers of this type were not observed neither in PbWO_4:Mo nor in PbWO_4:La(Y) crystals. The recombination processes of thermally released holes with electrons stored at different traps, including Pb^+ - WO_3 and (MoO_4)^3- centers, are systematically studied by TSL. Thermal stability parameters are defined by ESR and TSL techniques for different O^- type defects.