Thermally modulated optically stimulated luminescence (TM-OSL) as a tool of trap parameter analysis

The methods of optically stimulated luminescence (OSL) measurements used until recently, used optical stimulation with a constant energy and a constant or linearly increased flux of stimulation photons. During such a stimulation the ratio of probabilities of the optical release of electrons from different traps is constant and it is hard to separate the signals of different origins. It was shown recently that advantageous changes of the probability ratio during the OSL experiments, and more information about traps can be obtained by optical stimulation with the increasing stimulation energy. This method, however, needs a strong tuneable light source that supplies a stable flux of photons and because of that it cannot find a wide application. Inducing the appropriate changes of the probabilities of the optical release of electrons from traps by increasing the sample temperature during the optical stimulation with a constant stimulation band do not face such obstacles. Such a stimulation can be realised by means of the standard OSL readers after a slight modification and offers the possibility for direct estimation of optical trap depth. The simulations of the OSL process during linear heating show that the experimental parameters such as the heating rate, the stimulation light intensity and the stimulation energy strongly affect the shape of the OSL curve and can be the very useful tools for the OSL process regulation. By this kind of stimulation one can reach very deep traps that are not detectable by thermoluminescence measurements below 500 degrees C. The resolution of the OSL signal originating from different traps is remarkable. (C) 2016 Elsevier B.V. All rights reserved.