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The epitaxial films grown by liquid-phase epitaxy (LPE) have found an application as scintillation screens with the development of the technique of microimages obtaining using hard X-rays. Lu2SiO5:Tb, Gd3Ga5O12:Tb and Gd3Ga5O12:Eu epitaxial films are already used for such screens [1]. Recently, studies of the stimulated scintillation emission depletion (STED) properties of Lu3Al5O12:Ce (0.07% at.), Lu2SiO5:Ce, Gd2.96Ce0.03Al3.14Ga1.86O12, Lu2SiO5:Tb (12% at.), Gd3Ga5O12:Eu (2.5% at.) single-crystalline films were carried out [2]. It was shown, that Lu2SiO5:Tb scintillating film and a 628 nm cw STED-laser is the most promising combination for stimulated scintillation emission depletion X-ray imaging [2,3].
Here we report the results of the study of the epitaxial growth, optical, photoluminescence and scintillation properties of (Pb,Gd)3(AlGa)5O12:Се films. The goal of the study was to determine the composition of the melt solution, which allows to grow films with maximal photoluminescence and light output.
The garnet films were grown on (111)-oriented single crystal Gd3Ga5O12 substrates by LPE from a supercooled PbO–B2O3 based melt solutions with gadolinium oxide (C(Gd2O3)) concentrations between 0.2 and 0.5 mol% in the mixture, C(CeO2) concentrations 0.2 and 0.3 mol% and C(Al2О3) concentrations between 2.1 and 4.5 mol%. Studies of the optical absorption of the grown films have shown that the decrease of the intensity of the absorption band of 5d2 level and the increase of the absorption in the region up to 360 nm occurs for films which were grown from a melt solution with С(Gd2O3)=0.5 mol%, С(СeO2)=0.2 mol% and C(Al2О3)= 4.5 mol%. The effect is attributed to the formation of Сe4+ centers, which energy levels are situated near the bottom of the conduction band. Photoluminescent studies have shown that the most intensive photoluminescence was observed in the Pb0.01Ce0.03Gd2.96Al3.14Ga1.86O12 film which was grown from the melt solution with С(СeO2)=0.2 mol%, С(Gd2O3)=0.4 mol% and C(Al2О3)= 4.5 mol%. The cathodoluminescence decay curve for this film was fitted by triple-exponential decay law with parameters t1=2.1 ns (2%), t2 =24.9 ns (30%) and t3=61.0 (68%). The mean scintillation decay time in this film was 43 ns. The cathodoluminescence light output was estimated relatively to that of the well-known scintillator LYSO:Ce. The values were obtained: of ~ 51500 photon/MeV under electron excitation at 80-120 keV and ~20000 photon/MeV under the Radio Isotope source excitation at 32 keV.
1. Douissard P.-A., Cecilia A., Martin Th. Chevalier V., Couchaud M., Baumbach T., Dupre K., Kuehbacher M., Rack A. J. Synchrotron Rad., 17, 571 (2010).
2. Alekhin M.S., Renger J., Kasperczyk M., Douissard P.-A., Martin T., Zorenko Y., Vasil’ev D. A., Stiefel M., Novotny L., Stampanoni M. J. Optics express, 25, 1251 (2017).
3. Alekhin M.S., Patton G., Dujardin C., Douissard P.-A., Lebugle M., Novotny L., Stampanoni M. J. Optics express, 25, 654 (2017).
