ИСТИНА

The garnet films grown by liquid-phase epitaxy (LPE) can be applied as scintillation screens for visualization of X-ray images because of their excellent scintillation properties [1]. Here we report the results of the epitaxial growth of (Pb,Gd)3(Al,Ga)5O12:Се and (Bi,Gd)3(Al,Ga)5O12:Се epitaxial films and their optical properties. The goal of the study was to compare the optical properties of Gd3(Al,Ga)5O12:Ce films grown from Pb- or Bi-сontaining melt solutions. The garnet films were grown on single crystal Gd3Ga5O12, Gd3(Al,Ga)5O12 and Y3Ga5O12 substrates by LPE from a supercooled PbO–B2O3 and Bi2O3–B2O3 based melt solutions. Studies of the optical absorption of the grown films showed the presence of the absorption bands related to Pb2+, Bi3+, Ce3+, and Pt3+ ions. It was found that with a variation of the Al/Ga ratio in the film composition, there is a shift of the absorption bands related to Ce3+ ion. An increase in the concentration ratio Al/Ga in (Pb,Gd)3(Al,Ga)5O12:Се films from 0 to 2.18 leads to a red shift of the absorption band of the 5d1 level by 17 nm. Similar red shift of the Ce (5d1) absorption band by 43 nm was observed in the (Bi,Gd)3(Al,Ga)5O12:Се films with complete substitution of Ga with Al. The luminescence of Ce3+ was detected under excitation at 340, 430 nm in the (Pb,Gd)3(Al,Ga)5O12:Се films, at 430 nm in the (Bi,Gd)3(Al,Ga)5O12:Се films and at 460 nm in the (Bi,Gd)3Al5O12:Се films. Also in the (Bi,Gd)3(Al,Ga)5O12:Се films the 480 nm emission band with excitation maximum at 270 and 305 nm was observed and ascribed to Bi3+ clusters. The emission band at 820 nm was observed in the (Bi,Gd)3(Al,Ga)5O12:Се films. The origin of this band is discussed. The scintillation properties of the grown films were studied. The pulsed cathodoluminescence yield of the most intensive Pb0.01Ce0.02Gd2.97Al3.13Ga1.87O12 film was around 43100 photons/MeV and scintillation light yield was around 20000 photons/MeV under excitation from 133 Ba source. The pulsed cathodoluminescence decay times of this film were 1.8 (1%), 24 (25%), and 60 ns (74%) and scintillation decay times were 3.9 (7%), and 43.6 ns (93%).