Structurally defective cerium doped lutetium–yttrium oxyorthosilicates for optically stimulated luminescence imaging devices

Abstract

The paper reports experimental data concerning the feasibility of structurally defective cerium doped Lu_1.8Y_0.2SiO₅ oxyorthosilicates (Ce:LYSO) as optical stimulated luminescence (OSL) devices with emission at the Ce³⁺ recombination sites. The total OSL signal was evaluated as a function of continuous irradiation at 514.5 nm and compared to the curve obtained with a commercial C:Al₂O₃ sample. By assuming a single type of trap and a single recombination centre model for the OSL mechanism, the photoionization cross-section was estimated to be 1.7 × 10⁻¹⁷ cm². The stimulation spectrum of the OSL signal evidences a single maximum at about 470 nm and a smooth decrease down to 650 nm. The recombination mechanism as well as the nature of the trapping site was studied by means of thermo-stimulated luminescence (TSL) measurements and analysed according to the generalized order kinetics model. The results confirm a single type of trap and a thermally activated tunnelling mechanism between the electrons trapped in the oxygen vacancies and holes localized at the Ce³⁺ centres. The analysis is further confirmed by TSL measurements after illumination with monochromatic lights in the range of the OSL stimulation spectrum. Finally, due to the high localization of trapping sites and recombination centres, we propose cerium doped oxyorthosilicates as efficient OSL imaging devices and UV based optical data storage materials: direct applications of defective Ce:LYSO as OSL imaging devices are shown.