Epitaxial Growth of LuAG:Ce and LuAG:Ce,Pr Films and Their Scintillation Properties

We performed the growth by Liquid Phase Epitaxy (LPE) of Ce and Ce-Pr doped Lu₃Al₅O₁₂ (LuAG) Single Crystalline Films (SCFs) onto LuAG and Y₃Al₅O₁₂ (YAG) substrates. The structural properties of LuAG:Ce and LuAG:Ce,Pr SCFs were examined by X-ray diffraction. The optical properties of the SCFs were studied through cathodoluminescence (CL) spectra, scintillation Light Yield (LY), decay kinetic under <inline-formula> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula>–particle (Pu²³⁹) excitation, X-ray excited luminescence, thermostimulated luminescence (TSL) and afterglow measurements. The SCFs grown on LuAG substrates displayed good surface quality and structural perfection, whereas the SCFs grown on YAG substrates showed a rough surface and poorer crystalline quality, due to a large lattice mismatch between the film and the substrate (0.82%). Under <inline-formula> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula>-particle excitation, the LY of LuAG:Ce SCF exceeded by 2 times that of the best YAG:Ce SCF sample used as reference. Under X-ray excitation, the LuAG:Ce SCF with optimized Ce concentration showed LY close (77%) to a reference YAG:Ce Single Crystal (SC) scintillator. The afterglow of LuAG:Ce and LuAG:Ce,Pr SCFs was lower (by 1 decade) than that of the tested reference LuAG:Ce SC. However there is not a complete suppression of the afterglow at room temperature (RT), despite the fact that the SCFs present much lower concentration of antisite and vacancy type defects than their SC counterparts. This can be explained by the presence in the films of other trap centers responsible for TSL above RT.