49 research outputs found
Effect of the energy transfer in multicomponent garnet single crystal scintillators
Luminescence processes in the undoped and Pr3+-doped (Gd,RE)3(Ga,Al)5O12, RE = Lu,Y, multicomponent garnets are studied by time-resolved photoluminescence spectroscopy. Energy transfer processes between Pr3+ and Gd3+ causing significant deterioration of the scintillation performance are considered in detail. As is shown in current work, an overlap of the 5d1â3H4 emission transition of Pr3+ and 8Sâ6Px absorption transition of Gd3+ results in unwanted depletion of Pr3+ 5d1 excited state and is further intensified by the concentration quenching in the Gd3+-sublattice. This process explains a drastic decrease of light yield in Pr3+-doped Gd3+-containing multicomponent garnets observed in a previous work
Growth and luminescent properties of :Ce single crystalline films
The work is dedicated to the development of scintillating screens based on single crystalline films (SCF) of Ce doped LuâYâAl perovskites grown by the liquid phase epitaxy method. We show in this work that Lu1âxYxAP:Ce SCF with very good structural and optical perfection can be grown from the PbO-based flux onto YAP substrates in all range of x-values. We also found the Lu1âxYxAP:Ce SCF can be crystallized by LPE method from the lead free BaOâB2O3âBaF2 flux onto YAP substrates in the range of x values up to 0.4 formula units
Temperature dependence of the optical absorption coefficient of microcrystalline silicon
The optical absorption coefficient of amorphous and microcrystalline silicon was determined in a spectral range 400-3100 nm and a temperature range 77-350 K. Transmittance measurement and Fourier transform photocurrent spectroscopy were used. The measured data served as an input for our optical model of amorphous/microcrystalline tandem solar cell. Differences in the current generated in the amorphous and microcrystalline parts were computed, for an operating temperature between -20°C and +80°C. Optical spectra of microcrystalline silicon were compared to the spectrum of silicon on sapphire (without hydrogen and hydrogenated) and the observed difference was interpreted in terms of a different density of defects and higher disorder of microcrystalline Si. © 2004 Elsevier B.V. All rights reserved