Fyzikální ústav Akademie věd ČR

In the field of complex oxide scintillators the tungstates and doped aluminum perovskites (REAlO3), garnets (RE3Al5O12) and orthosilicates (RE2SiO5) are systematically studied in the form of single crystals, optical ceramics or thin films prepared by the liquid phase epitaxy (LPE), Fig. 1. We focus on the point defects which give rise to trapping levels in the material forbidden gap. Understanding the nature and role of such defects in the scintillation mechanism and their relation to the manufacturing technology enables further optimization of these materials. LPE is perspective technology for manufacturing thin scintillation detectors used for 2D imaging with high (submicron) resolution. We have characterized a new material system based on LuAG:Ce garnet [1]. We studied in detail a tunneling mechanism in the radiative recombination of the Ce-doped orthosilicates [2]. With the help of correlated thermostimulated luminescence and electron paramagnetic resonance (EPR) experiments we determined five variants of the hole O- and four variants of electron F+ centers [3]. We also calculated energy depths and frequency factors of all hole traps and estimated their lifetime at room temperature [5]. EPR measurements evidenced the hole self-trapping in CdWO4 structure [5]. A comparison of luminescence and scintillation kinetics in the Pr-doped garnets and orthosilicates as well as evaluation of their application potential was reported in [6]. An invited feature article [7] provides a survey of the state-of-art in the field of defects and trapping states in complex oxide scintillators..

1. P. Prusa, T. Cechak , J. A. Mares, M. Nikl, A. Beitlerova, N. Solovieva, Yu. V. Zorenko, V. I. Gorbenko, J. Tous, K. Blazek, Appl. Phys. Letters 92, 041903 (2008).
2. A. Vedda, M. Nikl, M. Fasoli, E. Mihokova , J. Pejchal, M. Dusek, G. Ren, C.R. Stanek, K. J. McClellan, D.D. Byle, Phys. Rev. B 78, 195123 (2008). r,
3. V.V. Laguta, M. Nikl, A. Vedda, E. Mihokova, J. Rosa, K. Blazek, Phys. Rev. B 80 045114 (2009).
4. A. Vedda, M. Fasoli, M. Nikl, V.V. Laguta, E. Mihokova, J. Pejchal, A. Yoshikawa, M. Zhuravleva, Phys. Rev. B 80, 045113 (9 pp) (2009).
5. V.V. Laguta, M. Nikl, J. Rosa, B.V. Grinyov, L.L. Nagornaya, I.A. Tupitsina, J. Appl. Phys. 104, 103525 (2008).
6. J. Pejchal, M. Nikl, E. Mihóková, J. A. Mareš, A. Yoshikawa, H. Ogino, K. M. Schillemat, A Krasnikov, A. Vedda, K. Nejezchleb and V. Múčka, J. Phys. D: Appl. Phys. 42 (2009) 055117
7. M. Nikl, V.V. Laguta and A. Vedda, (invited feature article) Phys. Stat. sol. (b) 245, 1701-1722 (2008).