Luminescence and energy transfer in CsLaSiS4 single crystals doped with Tb3+ and Ce3+ ions

Abstract

CsLaSiS₄ single crystals doped with Tb³⁺ and co-doped with Ce³⁺, Tb³⁺ ions were obtained by a high-temperature flux synthesis. XRD data demonstrate that the samples crystallize in the orthorhombic P_nma space group without additional reflections belonging to the impurity phases. Low-temperature luminescent spectroscopy methods have been used to study the efficiency of radiative transitions and energy transfer between Ce³⁺ and Tb³⁺ ions. Additionally, the effect of irradiation with protons with an energy of 18 MeV from a cyclotron was studied. Spectral-kinetic measurements of pulsed cathodo- and photoluminescence of samples co-doped with Ce³⁺ and Tb³⁺ revealed bidirectional energy transfer processes between these ions, the parameters of nonradiative energy transfer Ce³⁺ → Tb³⁺ were determined. The effect of concentration quenching is observed in undoped CsTbSiS₄. The method of low-temperature thermally stimulated luminescence and the kinetics of pulsed cathodoluminescence indicate a high concentration of "shallow" carrier trapping centers in doped samples. When irradiating CsLaSiS₄:0.5%Ce sample with protons, both the low-temperature emission of self-trapped excitons (STE) and the energy transfer STE → Ce³⁺ decrease, the luminescence yield of defect-bound excitons (DBE) also decreases compared to the emission of Ce³⁺ ions, and defects are mainly formed, which are the centers of nonradiative recombination of band charge carriers.