Reliability of trap-filling parameters read from OSL dose-response curves measured by procedures with sensitivity correction

Abstract

As is known from the early stimulated luminescence studies, dose-response curves (DRCs) are not consistent with the curves of the dependence of the electron concentration in the traps on the irradiation dose delivered to a crystal, even for a system consisting of one trap and one recombination centre. However, for the optically stimulated luminescence (OSL) signal originating from more complex trap and recombination centre systems, it is often observed that the DRC can be described by a simple single saturating exponential (SSE) or a double saturating exponential (DSE) function. Using simulations, we show that although good fit compliance can often be achieved, the parameters obtained only in some cases correctly describe the relationship between the occupancy of individual traps and the dose. Simulations performed for the DRC construction procedure included a step allowing for the correction of possible changes in sensitivity. A model of two traps active in the OSL process and two recombination centres was tested. The modelling shows that the results of the DRC analysis using SSE functions strongly depend not only on the relationship of the trapping probability coefficients of traps but also on their concentrations and the concentrations of recombination centres. The shape of the DRC, and therefore the fitting parameters, also change with the annealing temperature used in the DRC measurement protocol.