Simulations of time-resolved photoluminescence experiments in α-Al2O3:C

Abstract

This paper presents simulations of time-resolved photoluminescence (TR-PL) experiments in α-Al2O3:C, which is one of the main dosimetric materials. During TR-PL experiments, short pulses of UV-light are followed by relaxation periods of the charge carriers. The model used in these simulations was previously used to explain radioluminescence (RL), thermoluminescence (TL) and photoluminescence (PL) experiments for this material, and is based on optical and thermal ionizations of excited F-centers. There are no published simulations of TR-PL experiments in this important dosimetric material in the literature. In this paper, we present new simulations using two slightly different versions of the model. In the first original version of the model, thermal quenching is explained via thermal ionization of the recombination centers. In the new proposed modified version of the model, thermal quenching is described by a Mott–Seitz type of mechanism, based on competitions between radiative and radiationless electronic transitions occurring within the recombination center. We simulate a typical TR-PL experiment in Al2O3:C at different stimulation temperatures, and compare the simulation results with available experimental data. It is found that both versions of the model provide a reasonable quantitative description of the luminescence lifetime and luminescence intensity as a function of the stimulation temperature. However, very significant differences between the two models are found for the behavior of the simulated integrated thermoluminescence (TL) and thermally stimulated conductivity (TSC) as a function of the heating rate used during such experiments. Only the results from the modified version of the model, (which is based on Mott–Seitz mechanism), are in good agreement with previously reported experimental results. The two models also predict very different behaviors for the dependence of the optically integrated stimulated luminescence (OSL) and TSC signals, as a function of the stimulation temperature. The results from the two models suggest that it may be possible to decide between the two mechanisms of thermal quenching in this material, by carrying out accurate measurements of the TL, TSC and OSL signals under different experimental conditions. The effect of shallow traps on the luminescence lifetimes is also studied and compared with available experimental data.