The fast development of 2D/3D micro-imaging techniques using X-ray radiation strongly demands single crystalline film (SCF) scintillating screens with high ability of X-ray absorption and submicron spatial resolution [1]. Our report presents the results of pioneer research directed on the creation of new types of screens based on the SCF of Ce doped multi-component (Gd,Y,La,Lu)₃(Al,Ga,Sc)₅O₁₂ garnets by liquid phase epitaxy (LPE) method. In our work we try to applied the combination of the “band-gap engineering” [2] and “5d-level positioning” strategies [3] to the basic materials - the Ce doped Y₃Al₅O₁₂ (YAG) and Lu₃Al₅O₁₂ (LuAG) garnets, using the alloying with Sc and Ga ions in the octahedral positions and Gd and La ions into the dodecahedral position of the LuAG and YAG hosts.

The main task in the growth SCF based on the multi-component garnets by LPE method is the decreasing of the misfit Δa between the lattices of SCF and substrate to condition of the SCF growth (Δa <0.1 % [4]). That can be achieved by the respective choice of substrate and SCF cation content. Apart the YAG substrate with lattice constant a=12.01 Ǻ, typically using for growth of YAG and LuAG based SCF, we consider also in our work the possibility of SCF crystallization by LPE method onto Gd₃Ga₅O₁₂ (GGG) substrates with a=12.38 Ǻ. Namely, we successfully crystallized of the Ce-doped of the SCF of Lu_3-xGd_xAl₅O₁₂ and Lu₃Sc₂Al₃O₁₂ garnets onto YAG substrates as well as the SCF of Gd_3-x(Y,Lu)_xGa_5-yAl_yO₁₂, Gd_3-x(Y,Lu)_xSc₂Al₃O₁₂ and Lu_3-xLa_x(Ga,Sc)₂Al₃O₁₂ garnets onto GGG substrates using the typical PbO-B₂O₃ flux. The values of x and y in compositions of these garnets were changed from x=0 to 1.5 formula units.

The SCF were characterized by XRD and content analyses as well as by the absorption and cathodoluminescence (CL) spectra, light yield (LY) of CL under e-beam excitation and scintillation LY under excitation by α–particles of Pu²³⁹ (5.15 MeV) source. We found that from all SCF, grown onto YAG substrates, the best LY possess the SCF of Ce doped Lu_3-xGd_xAl₅O₁₂ garnets at x=0.8-1.0. From all studied SCF, grown onto GGG substrates, the best LY possess the SCF of Gd_3-xY_xSc₂Al₃O₁₂ and Gd_3-xLu_xSc₂Al₃O₁₂ garnets at x=0.5-0.75. We also noted the significantly large content of Pb²⁺ flux related impurity and their higher influence on the LY of the Ce doped SCF of multi-component garnets, grown on the GGG substrates, in comparison with SCF of garnets, grown on the YAG substrates.

For determination of the fundamental optical characteristic of studied garnets (the band gap values, the positions of Ce³⁺ f-d levels relatively band gap extremes; the energy formation of excitons bound with the Ce ions), the luminescent spectroscopy of (Gd,La,Y,Lu)₃(AlGaSc)₅O₁₂ SCF were performed at the Superlumi station, HASYLAB, DESY under excitation by synchrotron radiation in 3.7-25 eV range.

[1] Т. Мartin, A. Koch, Journal of Synchrotron Radiation, 13, 180 (2006).

[2] M. Fasoli, A. Vedda, M. Nikl, C. Jiang, et all., Phys. Rev.,B 84, 081102 (2011).

[3] K. Kamada, T. Endo, K. Tsutumi, T. Yanagida, et all., Cryst. Growth Des., 11, 4484 (2011).

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