ИСТИНА

Here we report the results on the growth, optical and scintillation properties of Ce-doped (Pb,Gd)3(Al,Ga)5O12 epitaxial garnet films. 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 increase of aluminum concentration shifts the absorption band of the 5d1 level to longer wavelengths and the absorption band of 5d2 level - to shorter wavelengths. The films grown from the melt solution with C(Gd2O3)=0.5 mol% in the mixture have shown broadening of the absorption band of the 5d2 level. The effect is attributed to the formation of Сe4+ centers near the bottom of the conduction band. The emission spectra of the Ce-doped (Pb,Gd)3(Al,Ga)5O12 films at interband excitation contained a broad luminescence band in the 475-700 nm range with maximum at 532 nm (2.33 eV). The most intensive luminescence was observed in the Pb0.01Ce0.03Gd2.96Al3.14Ga1.86O12 film which was grown from melt solution with С(СeO2)=0.2 mol% and С(Gd2O3)=0.4 mol%. The luminescence decay curve for this film was modeled 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 light output was ~ 25000 photon/MeV by electron excitation at 50 keV and ~20000 photon/MeV by the Radio Isotope source at 32 keV.