Electron and hole trapping in irradiated PbBr2:Tl single crystals

Several hole trapped centres, namely Tl2+, self-trapped hole and A-type centres, were observed by ESR in PbBr2:Tl single crystals after X-ray irradiation at 77 K. The corresponding spectra are visible up to 200 K for all three defect centres. The STH centres are observed at higher temperatures than in the undoped PbBr2 single crystals, probably due to the stabilising effect of the Tl+ impurities. The ESR parameters of the Tl2+ centre point to stronger covalency effects in PbBr2 than in the isostructural PbCl2 crystals. All hole trapped centres started decaying around 160 K, probably due to recombination with nonparamagnetic electron trapped centres. Besides a small concentration of self-trapped electron centres, no other electron trapped centres were observed.