The nature and mechanism of charging of electron traps in Lu2SiO5 : Ce3+ crystals

摘要

Investigation of the thermoluminescence (TL) properties depending on the temperature, UV irradiation dose, and activator ion concentration in Lu2SiO5:Ce3+ (LSO:Ce) crystals and measurements of the decay of recombination radiation during photostimulated release of the excitation energy accumulated in these crystals showed that a part of Ce3+ impurity ions exhibit ionization leading to the injection of electrons into the conduction band. The conduction band of a LSO:Ce crystal is involved in two opposite processes: the charging of electron traps and the recombination of electrons with Ce4+ ions. The transport of electrons to the traps has a diffusion character: electrons possess a significant mobility [D(315 K) = 10(-3) cm(2)/s] and can diffuse away from the donor ions to distances exceeding the lattice parameter of the crystal. The results of experiments with controlled atomic packing of LSO:Ce nanoclusters unambiguously demonstrated the key role of the structure of oxyorthosilicates in the formation of electron traps. The existing two-center model does not provide adequate description of the properties of electron traps and TL in LSO:Ce crystals. (C) 2004 MAIK "Nauka/Interperiodica".