Single Crystalline Films of Ce 3+ -Doped Y 3 Mg x Si y Al 5-x-y O 12 Garnets: Crystallization, Optical, and Photocurrent Properties.

This research focuses on LPE growth, and the examination of the optical and photovoltaic properties of single crystalline film (SCF) phosphors based on Ce 3+ -doped Y 3 Mg x Si y Al 5-x-y O 12 garnets with Mg and Si contents in x = 0-0.345 and y = 0-0.31 ranges. The absorbance, luminescence, scintillation, and photocurrent properties of Y 3 Mg x Si y Al 5-x-y O 12 :Ce SCFs were examined in comparison with Y 3 Al 5 O 12 :Ce (YAG:Ce) counterpart. Especially prepared YAG:Ce SCFs with a low (x, y < 0.1) concentration of Mg 2+ and Mg 2+ -Si 4+ codopants also showed a photocurrent that increased with rising Mg 2+ and Si 4+ concentrations. Mg 2+ excess was systematically present in as-grown Y 3 Mg x Si y Al 5-x-y O 12 :Ce SCFs. The as-grown SCFs of these garnets under the excitation of α-particles had a low light yield (LY) and a fast scintillation response with a decay time in the ns range due to producing the Ce 4+ ions as compensators for the Mg 2+ excess. The Ce 4+ dopant recharged to the Ce 3+ state after SCF annealing at T > 1000 °C in a reducing atmosphere (95%N 2 + 5%H 2 ). Annealed SCF samples exhibited an LY of around 42% and similar scintillation decay kinetics to those of the YAG:Ce SCF counterpart. The photoluminescence studies of Y 3 Mg x Si y Al 5-x-y O 12 :Ce SCFs provide evidence for Ce 3+ multicenter formation and the presence of an energy transfer between various Ce 3+ multicenters. The Ce 3+ multicenters possessed variable crystal field strengths in the nonequivalent dodecahedral sites of the garnet host due to the substitution of the octahedral positions by Mg 2+ and the tetrahedral positions by Si 4+ . In comparison with YAG:Ce SCF, the Ce 3+ luminescence spectra of Y 3 Mg x Si y Al 5-x-y O 12 :Ce SCFs greatly expanded in the red region. Using these beneficial trends of changes in the optical and photocurrent properties of Y 3 Mg x Si y Al 5-x-y O 12 :Ce garnets as a result of Mg 2+ and Si 4+ alloying, a new generation of SCF converters for white LEDs, photovoltaics, and scintillators could be developed.