Four types of electron traps in PbWO4, based on regular W sites perturbed by oxygen vacancies, are identified by electron spin resonance (ESR). The analysis of the ESR spectra parameters (g-factor values and principal-axes orientations) shows that the revealed centers are (WO3)(-) vacancy-containing complex anions associated with a defect in the Pb sublattice: (WO3)(-)-A(Pb) complexes. Two of the centers (W-1 and W-2) are thermally stable up to 350-370 K, while the other two (W-3 and W-4) are stable only up to 270-290 K. Above these temperatures the trapped electrons become free and recombine with localized holes, giving rise to a composite TSL glow peak at Tapproximate to323 K (characterized by a trap depth of 0.9 eV evaluated by the initial rise method) and to a weaker TSL structure at Tapproximate to365 K. The correspondence between (WO3)(-)-A(Pb) centers and TSL peaks is supported by their similar room temperature time decays, and by the similar dependences of ESR and TSL signals upon annealing treatments. A scheme of local electronic levels in the band gap of PbWO4 is proposed.
Laguta, V., Martini, M., Vedda, A., Rosetta, E., Nikl, M., Mihokova, E., et al. (2003). Electron traps related to oxygen vacancies in PbWO4. PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS, 67(20), 205102.1-205102.8 [10.1103/PhysRevB.67.205102].
Electron traps related to oxygen vacancies in PbWO4
MARTINI, MARCO;VEDDA, ANNA GRAZIELLA;
2003
Abstract
Four types of electron traps in PbWO4, based on regular W sites perturbed by oxygen vacancies, are identified by electron spin resonance (ESR). The analysis of the ESR spectra parameters (g-factor values and principal-axes orientations) shows that the revealed centers are (WO3)(-) vacancy-containing complex anions associated with a defect in the Pb sublattice: (WO3)(-)-A(Pb) complexes. Two of the centers (W-1 and W-2) are thermally stable up to 350-370 K, while the other two (W-3 and W-4) are stable only up to 270-290 K. Above these temperatures the trapped electrons become free and recombine with localized holes, giving rise to a composite TSL glow peak at Tapproximate to323 K (characterized by a trap depth of 0.9 eV evaluated by the initial rise method) and to a weaker TSL structure at Tapproximate to365 K. The correspondence between (WO3)(-)-A(Pb) centers and TSL peaks is supported by their similar room temperature time decays, and by the similar dependences of ESR and TSL signals upon annealing treatments. A scheme of local electronic levels in the band gap of PbWO4 is proposed.
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