Investigation of photoluminescence in CaGa₂S₄:Eu this films irradiated by γ guanta

In order to create radiation centers in the CaGa₂S₄ compound, oxides and fluorides of the thin-layer elements europium, cerium, and others are introduced into it during the synthesis of that compound. Studies show that the interaction of the cerium atom with the europium enhances the radiation intensity in the CaGa₂S₄ compound. This means that the cerium atom acts as a sensitizer for Eu in the compound. In other words, the radiation emitted by cerium in the CaGa₂S₄ compound excites the europium element. CaGa₂S₄, Eu, CaGa₂S₄:Eu thin films were obtained on quartz glass by the thermal evaporation method. Before evaporation, the CaGa₂S₄: Eu compound was synthesized at 10000C as a result of a solid-state reaction based on CaS and Ca₂S₃ compounds. This compound has n-type conductivity, that is, electrons are the electric charge carriers in it. The Ga₂S₃ compound has a cubic structure. The resulting polycrystalline compound evaporated and transferred to the substrate. The thickness of the obtained amorphous thin layer was 1-5 micro meter. The layer was annealed at 2000C in order to partially fix the defects. The effect of the received CaGa₂S₄: Eu layer on the photoluminescence properties of defects and dopant atoms was carried out at temperatures T=77 and 300K before and after radiation. Radiation with γquanta was performed in a Cobalt 60 device. Pre-irradiation studies show that the introduction of a Eu-doped atom enhances the photoluminescence emission in CaGa₂S₄ thin film. The reason for this may be the process of adjusting of structural defects as a result of radiation. The Eu atom creates a local level (activator) in the band gap of the crystal, and as a result of excitation of the activator, a band hν_max = 2.35 eV is observed. The intensity of the band and the width of the spectrum (0.14-0.18 eV) increase at a radiation dose of 5 Mrad. At the value of 500 krad of radiation, the radiation intensity of the luminescence band decreases compared to the original sample, and two maxima are observed This indicates that radiation centers of the anionic and cationic types are formed as a result of the dissociation of complexes as a result of the dopant ion and the specific interaction of radiation defects. At higher values (10 Mrad) of the radiation dose, a band of low intensity hν_max = 2.35 eV is observed in the radiation spectrum. The results obtained during the experiment show that the partially polycrystallized layer doped with Eu-doped atom emits high-intensity photoluminescence radiation in the visible region of the spectrum, and its intensity can be purposefully controlled by the influence of gamma quantates.