Localized excitons and defects in PbWO4 single crystals:: a luminescence and photo-thermally stimulated disintegration study

Luminescence from the exciton- and defect-related states and photo-thermally stimulated disintegration of these states under selective UV irradiation were studied in the PbWO4:Mo, Ce crystal and compared with the characteristics of other undoped and doped PbWO4 crystals of different origin. For the first time, various localized exciton states were identified and their decay into stable defects was found. Different positions, halfwidths and temperature dependences were observed for the blue emission spectrum in different PbWO4 crystals and explained by the presence of strongly overlapping emission bands of the WO42--type self-trapped and localized excitons. Binding energies of the self-trapped and localized exciton states were calculated. The dominant thermally stimulated luminescence peaks, created in the PbWO4: Mo, Ce crystal by the UV radiation, are located at 110, 202 and 247 K. The related trap depths were calculated using the initial rise method. It was concluded that under irradiation in the exciton absorption region, defects are mainly created due to the disintegration of the localized exciton states, which occurs without release of free charge carriers. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim