Thermally-assisted optically stimulated luminescence from deep electron traps in α-Al2O3:C,Mg

Highlights: • Thermally-assisted OSL (TA-OSL) in α-Al₂O₃:C,Mg has been studied. • The maximum TA-OSL intensity was found at the measurement of 160 °C. • The concentration of deep traps in α-Al₂O₃:C,Mg is not as high as in α-Al₂O₃:C. • The TA-OSL dose response is sublinear from 25 to 150 Gy but saturates thereafter. • The thermal-assistance energy of the deep trap is 0.667 ± 0.006 eV. We report thermally-assisted optically stimulated luminescence (TA-OSL) in α-Al₂O₃:C,Mg. The OSL was measured at elevated temperatures between 50 and 240 °C from a sample preheated to 500 °C after irradiation to 100 Gy. That OSL could be measured even after the preheating is direct evidence of the existence of deep electron traps in α-Al₂O₃:C,Mg. The TA-OSL intensity goes through a peak with measurement temperature. The initial increase is ascribed to thermal assistance to optical stimulation whereas the subsequent decrease in intensity is deduced to reflect increasing incidences of non-radiative recombination, that is, thermal quenching. The activation energy for thermal assistance corresponding to a deep electron trap was estimated as 0.667 ± 0.006 eV whereas the activation energy for thermal quenching was calculated as 0.90 ± 0.04 eV. The intensity of the TA-OSL was also found to increase with irradiation dose. The dose response is sublinear from 25 to 150 Gy but saturates with further increase of dose. The TA-OSL dose response has been discussed by considering the competition for charges at the deep traps. This study incidentally shows that TA-OSL can be effectively used in dosimetry involving large doses.