Origin of slow low-temperature luminescence in undoped and Ce-doped Y2SiO5and Lu2SiO5single crystals

Abstract

At 4.2–300 K, the steady-state and time-resolved emission and excitation spectra as well as the luminescence decay kinetics in the 10 μs–10 s time range are studied for the undoped and Ce3+-doped single crystals of Y2SiO5 and Lu2SiO5. At low temperatures, a broad intrinsic emission band located at 2.55 eV in Y2SiO5 and 2.58 eV in Lu2SiO5 is observed in the luminescence spectra of all the crystals studied under excitation in the charge-transfer absorption region (with Eexc > 4.2 eV). This emission reveals the slow non-exponential decay kinetics characteristic for tunneling recombination processes. In the slow decay kinetics of the low-temperature luminescence of Ce3+-doped crystals, both the multi-exponential and the non-exponential decay stages are detected. The origin of the defects, responsible for the undesirable slow low-temperature luminescence of the undoped and Ce3+-doped Y2SiO5 and Lu2SiO5 crystals is considered. A new mechanism of the processes, resulting in the appearance of different luminescence decay stages, is proposed.