The single crystalline films (SCF) of undoped, Ce and Ce-Tb doped Y₂SiO₅ (YSO), Lu₂SiO₅ (LSO) and (Lu_xGd_1-x)₂SiO₅ (LGSO) orthosilicates with a thickness from 2.5 to 100 µm were prepared by the liquid phase epitaxy (LPE) method onto undoped YSO and LSO substrates with different orientation from melt-solution (MS) based on PbO-B₂O₃ flux. These SCF can be used as scintillating screens for 2D X-ray microimaging [1]. In case LSO and LGSO SCF growth onto YSO and LSO substrates we did not use any additional doping to reduce the misfit between the SCF and substrate lattice parameters.

Luminescence of undoped YSO and LSO SCF is caused by the UV emission of Pb²⁺ flux impurity in the bands at 365 and 348 nm, respectively, related to the ³P_1,0-¹S₀ transitions, and by a visible band at 445 and 438 nm, ascribed to luminescence of excitons localised around the Pb²⁺ centers.

The luminescent properties of YSO:Ce, LSO:Ce and LGSO:Ce SCFs were compared with YSO, LYSO and LSO:Ce single crystal (SC). We found that the luminescence of YSO:Ce and LSO:Ce SCF caused by the 5d₁-4f radiative transition of Ce³⁺ ions is red-shifted in comparison with SC counterparts. This shift can be caused by (1) different relative occupancy of Y1/Lu1 and Y2/Lu2 sites of YSO and LSO hosts by Ce³⁺ ions in the case of SCF and SC growth due to very different temperatures for SC (2100^oC) and SCF (~1000^oC) crystallization; (2) luminescence of Pb²⁺ centers, overlapping with the emission of Ce³⁺ ions. We also found that the emission spectrum of LGSO:Ce SCF is systematically red-shifted with respect to spectrum of LSO:Ce SCF with increasing the Gd content in range of 0-0.7 formula units due to the increasing of the relative content of Ce2 centers in LGSO host. Such a red shit of the luminescence spectra of LGSO:Ce SCF is accompanied by decreasing their light yield (LY) down to 65 % for Lu_0.3Gd_0.7SO:Ce SCF in comparison with LY of LSO:Ce SCF. We would like also to note that LGSO:Ce SCF, despite of lower LY in comparison with LSO:Ce, possess much higher signal/noise ratio due to drop of afterglow level by ~100 times, by analogy with SC [2]. Therefore, image contrast at X-ray visualization should be better with LGSO screens.

The LY of YSO:Ce and LSO:Ce SCF reaches the value equal to 95-145 % of that for a LSO:Ce SC under excitation by α–particles of Am²⁴¹ sources (5.5 MeV) but only ~40-60 % of the LY of high-quality LYSO:Ce SC. The lower LY of (Y,Lu,Gd)SO:Ce SCF with respect to the best SC analogues is caused by quenching induced by Pb²⁺ flux impurity. Therefore, the usage of the lead-free fluxes is strongly needed for crystallization by the LPE method of (Y.Lu,Gd)SO:Ce SCF scintillators to increase their LY.

[1] T. Martin, at al. IEEE TNS 56 (2009) 1412.

[2] O. Sidletskiy et al. Journal of Crystal Growth 312 (2010) 601-606

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/29582 must be provided.

1. Optimization of bottom heater parameters at growth of large BGO crystals by conventional czochralski method
2. Superheavy scintillators based on REAO₄ compounds (RE= rare earth element,  A= V, Ta and Nb)
3. Optimization of bottom heater parameters at growth of large BGO crystals by conventional Czochralski method
4. Development of novel scintillating screens based on thesingle crystalline films of Ce doped multi-component (Gd,Y,Lu,La)₃(Al,Ga,Sc)₅O₁₂ garnets by LPE method
5. ZnWO₄ films obtained by ion–beam sputtering and hydrothermal method
6. Comparison of LGSO:Ce scintillator crystals grown by micro-PD and Czochralski methods
7. Features of YAG crystal obtaining by Czochralski method using Mo crucibles
8. Light yield behavior in mixed oxide scintillation crystals