Delayed optically stimulated luminescence of Al 2 O 3 :Si,Ti phosphor

In some Al 2 O 3 samples, the OSL is seen to decay much more slowly that we would expect due to re-trapping of the released charge in shallow traps. The preliminary studies indicate that Al 2 O 3 :Si,Ti has some component of delayed optically stimulated luminescence (DOSL). Therefore, DOSL in this system has been investigated in detail and relative contribution of DOSL to the CW-OSL signal has been determined. Therefore, OSL readout has been performed at elevated temperatures (in the range 27-100°C) in order to eliminate the contribution of DOSL in the CW-OSL signal. The dependence of DOSL signal on readout temperature can be explained in terms of Arrhenius equation of thermally released charges from shallow traps. The total contribution of the DOSL to the CW-OSL intensity is estimated to be about 1.4%. Although the contribution of DOSL to the CW-OSL integral signal is much less, it is advisable that OSL measurements be performed at 75°C to avoid any contribution of DOSL signal to CW-OSL signal. The DOSL decay shows the second order exponential fit. The activation energy calculated for the trap responsible for DOSL is 0.5 ±0.04 eV.