Photoinduced Pb+ center in PbWO4: Electron spin resonance and thermally stimulated luminescence study - art. no. 165102

Electron traps based on regular Pb sites perturbed by oxygen vacancies (V-O ) in high purity undoped PbWO4 have been revealed and studied by electron s pin resonance (ESR) and thermally stimulated luminescence (TSL) measurement s. Detailed analysis of ESR spectra parameters (g factor, hyperfine, and su perhyperfine structures) along with the variation of the concentration afte r annealing in inert and oxygen atmospheres had shown that revealed centers are Pb+-V-O complexes. The Pb+-V-O centers are created in two ways: (i) by direct trapping of the electrons from the conduction band under x-ray or u ltraviolet irradiation at T<60 K; (ii) by retrapping of electrons freed fro m unperturbed (WO4)(3-) centers after irradiation at T<40 K, followed by he ating at T=60 K Above T approximate to 180 K, Pb+-VO centers are - thermall y ionized, giving rise to a TSL,glow peak due to the recombination of freed electrons with localized holes. The emission spectrum of the TSL features one band peaking at around 2.5 eV. The temperature dependence of both TSL a nd ESR intensities has been analyzed using a first order recombination mode l: the thermal ionization energy of Pb+ -V-O centers tuf ns out to be 0.55 eV. The role of Pb+-V-O centers in the processes, of carrier trapping and. recombination of nonequilibrium carriers in the PbWO4 lattice is briefly di scussed.