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Jary V.,Institute of Physics AS CRCukrovarnicka 10162 53PragueCzech Republic | Krasnikov A.,Institute of PhysicsUniversity of TartuRiia 14251014TartuEstonia | Nikl M.,Institute of Physics AS CRCukrovarnicka 10162 53PragueCzech Republic | Zazubovich S.,Institute of PhysicsUniversity of TartuRiia 14251014TartuEstonia
Physica Status Solidi (B) Basic Research | Year: 2014

At 4.2-300K, the steady-state and time-resolved emission and excitation spectra as well as the luminescence decay kinetics in the 10μs-10s time range are studied for the undoped and Ce3+-doped single crystals of Y2SiO5 and Lu2SiO5. At low temperatures, a broad intrinsic emission band located at 2.55eV in Y2SiO5 and 2.58eV in Lu2SiO5 is observed in the luminescence spectra of all the crystals studied under excitation in the charge-transfer absorption region (with Eexc>4.2eV). This emission reveals the slow non-exponential decay kinetics characteristic for tunneling recombination processes. In the slow decay kinetics of the low-temperature luminescence of Ce3+-doped crystals, both the multi-exponential and the non-exponential decay stages are detected. The origin of the defects, responsible for the undesirable slow low-temperature luminescence of the undoped and Ce3+-doped Y2SiO5 and Lu2SiO5 crystals is considered. A new mechanism of the processes, resulting in the appearance of different luminescence decay stages, is proposed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Buryi M.,Institute of Physics AS CRCukrovarnicka 10162 53PragueCzech Republic | Bohacek P.,Institute of Physics AS CRCukrovarnicka 10162 53PragueCzech Republic | Chernenko K.,Peter the Great Saint Petersburg Rolytechnic UniversityPolytekhnicheskaya 29195251Saint PetersburgRussia | Krasnikov A.,Institute of PhysicsUniversity of TartuRavila 14c50411TartuEstonia | And 4 more authors.
Physica Status Solidi (B) Basic Research | Year: 2016

For the first time, photoluminescence of PbWO4:Bi crystals with different bismuth contents is studied by the time-resolved spectroscopy methods at 4.2-300K. Photo-thermally stimulated processes of electron and hole centers creation under selective UV irradiation of the crystal in the 3-5eV energy range and the 4.2-200K temperature range are clarified, and the optically created electron and hole centers are identified by the thermally stimulated luminescence and electron spin resonance methods. The 2.2eV emission of PbWO4:Bi crystals, excited in the Bi3+-related absorption band overlapped with the exciton absorption band, is shown to be of an excitonic origin and is suggested to arise from the excitons of two types localized around two different Bi3+-related centers. No emission, arising from the electron transitions between the energy levels of Bi3+ ions, is observed. Photoexcitation of PbWO4:Bi crystals in the Bi3+-related absorption region results also in the creation of electron and hole centers. Three new paramagnetic centers are identified: (i) two holes trapped at two regular oxygen ions located close to a Bi3+ ion and a lead vacancy VPb (the (2O--Bi3+-VPb)-type hole centers); (ii) Bi4+ centers; and (iii) the O--type hole centers. The concentration of single (non-compensated) oxygen and lead vacancies as traps for electrons and holes, respectively, is found to be small. The processes resulting in the appearance of the Bi3+-related localized exciton emission and in the creation of Bi-related electron and hole centers are discussed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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