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.