Optical and Electron Paramagnetic Resonance Study of the Ce 3+ Luminescent Centers in Lu 2 SiO 5 :Ce Single Crystalline Films

The work presents the results of optical and electron paramagnetic resonance (EPR) investigations of Ce 3+ incorporation into Lu 2 SiO 5 single crystalline films (LSO:Ce SCFs), grown using the liquid phase epitaxy method. It also examines the conversion of Ce valence state as a result of the LSO:Ce SCF thermal treatment in reducing and oxygen-rich atmospheres. The EPR study revealed the presence of only one type of Ce 3+ center (Ce1), corresponding to the localization of Ce 3+ ions in 7-fold coordinated positions within the Lu 2 SiO 5 host. No spectra of Ce2 centers (6-fold coordinated Ce 3+ positions) were detected in the LSO:Ce SCF films, indicating their negligibly small concentration. High-temperature annealing of the as-grown films in air reduces the concentration of Ce 3+ ions to a level undetectable by EPR due to the Ce 3+ → Ce 4+ conversion. In contrast, thermal treatment in a 95%N 2 + 5%H 2 reducing atmosphere results in the opposite Ce 4+ → Ce 3+ conversion, substantially increasing the concentration of Ce 3+ . The oxidation/reduction treatment and Ce 3+ /Ce 4+ valence state change lead to notable variations in the scintillation light yield and decay kinetics of the LSO:Ce SCFs, offering a method to tune their scintillation figure of merit.