Four types of electron trap in PbWO4, based upon regular W sites perturbed by O vacancies, were identified by electron spin resonance. The analysis of the electron spin resonance spectra parameters (g-factor values and principal-axes orientations) showed that the revealed centers were (WO3)– vacancy-containing complex anions associated with a defect in the Pb sub-lattice: (WO3)–-APb complexes. Two of the centers (W1 and W2) were thermally stable up to 350–370K, while the other two (W3 and W4) were stable only up to between 270 and 290K. Above these temperatures, the trapped electrons became free and recombined with localized holes, giving rise to a composite TSL glow peak at about 323K (characterized by a trap depth of 0.9eV evaluated by the initial rise method) and to a weaker TSL structure at about 365K. The correspondence between (WO3)–-APb centers and TSL peaks was supported by their similar room temperature time decays, and by the similar dependences of electron spin resonance and TSL signals during annealing.

Electron Traps Related to Oxygen Vacancies in PbWO4. V.V.Laguta, M.Martini, A.Vedda, E.Rosetta, M.Nikl, E.Mihóková, J.Rosa, Y.Usuki: Physical Review B, 2003, 67[20], 205102 (8pp)