Defects in Ce-doped LuAG and YAG scintillation layers grown by liquid phase epitaxy Miroslav Kuc ˇera a, * , Karel Nitsch b , Martin Nikl b , Martin Hanus ˇ a a Charles University, Faculty of Mathematics and Physics, Ke Karlovu 5,12116 Prague 2, Czech Republic b Institute of Physic AS CR, Cukrovarnicka ´ 10, 16000 Prague 6, Czech Republic article info Article history: Received 17 August 2009 Received in revised form 1 December 2009 Accepted 13 December 2009 Keywords: YAG LuAG Ce-doping Garnet Liquid phase epitaxy Luminescence abstract The single crystalline Lu 3 Al 5 O 12 (LuAG) and Y 3 Al 5 O 12 (YAG) garnet layers doped by Ce 3þ ions were grown by the liquid phase epitaxy from the flux. The effect of the flux composition, growth conditions, and substrate polishing on the layer morphology, creation of defects, and on optical and emission properties of layers was studied. The defects typical of the epitaxial growth are discussed. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Thin single crystalline oxide layers doped by activator ions such as Ce 3þ can be used in high resolution scintillation screens (Martin and Koch, 2006). Compared to Czochralski grown single crystals, the layers prepared by the liquid phase epitaxy (LPE) are grown from a flux at much lower temperatures and hence with lower structural disorder and lower number of intrinsic defects. The garnet layers do not have antisite defects, where part of the Lu ions occupies the Al octahedral sites, (Zorenko et al., 2007). These defects form shallow traps in the gap and induce a slow component in the scintillation decay of LuAG single crystals (Nikl et al., 2007). On the other hand, various impurities can enter into the crystal lattice from the flux and some new defects specific to the LPE technology are induced during the growth. Furthermore, other factors inherent for epitaxial layers such as flux properties (composition, viscosity), growth conditions (growth temperature, supercooling, growth rate), substrate proper- ties (layer–substrate lattice match, defects in substrates such as dislocations or scratches arising from polishing) influence the quality of epitaxial layers and subsequently their scintillation properties. In view of that, various point defects can be created in layers. This can bring about a loss of energy due to nonradiative transitions and decrease of emission intensity. Here we report on some specific defects observed in epitaxial layers of yttrium and lutetium aluminum garnets, YAG and LuAG, doped by Ce 3þ activator ions. 2. Samples Undoped and Ce 3þ doped single crystalline YAG and LuAG epitaxial garnet layers were grown by the isothermal dipping LPE ontoYAG and LuAG substrates of (111) and (110) orientation. Three different fluxes, PbO–B 2 O 3 , BaO–B 2 O 3 –BaF 2 , and MoO 3 –Li 2 MoO 4 , respectively, were used with the goal to reduce the flux-related impurities and defects. Various compositions of each flux were used and from each composition a series of garnet layers were grown. The growth temperatures were between 930 and 1080  C and the layer thicknesses were in the range 2–25 mm. The layers were characterized using the X-ray diffraction, polarized optical microscopy, interference surface profilometry (3D surface profiler Zygo), optical absorption and photoluminescence (PL) spectroscopies. All the measurements were made at a room temperature. In this paper, only optical microscopy pictures and decay curves will be shown. The luminescence results will also be discussed in regard of typical defects involved in the LPE. 3. Results Good lattice match between the layer and the substrate is required in order to obtain good quality single crystalline layers. If * Corresponding author. E-mail address: miroslav.kucera@mff.cuni.cz (M. Kuc ˇera). Contents lists available at ScienceDirect Radiation Measurements journal homepage: www.elsevier.com/locate/radmeas ARTICLE IN PRESS 1350-4487/$ – see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.radmeas.2009.12.031 Radiation Measurements xxx (2010) 1–4 Please cite this article in press as: Kuc ˇera, M., et al., Defects in Ce-doped LuAG and YAG scintillation layers grown by liquid phase epitaxy, Radiation Measurements (2010), doi:10.1016/j.radmeas.2009.12.031