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Low-temperature thermoluminescence in TlGaS2 layered single crystals

Thermoluminescence (TL) measurements have been carried out on TlGaS2 layered single crystals in the temperature range of 10-300 K. After illuminating with blue light (similar to 470 nm) at 10 K, TL glow curves exhibited peaks around 23, 36, 58, 75 and 120 K when measured with a heating rate of 0.8 K/s. The observed peaks were analyzed using curve fitting, initial rise, and peak shape methods to determine the activation energies of the associated defect centers. Analyses have revealed the presence of five defect centers with activation energies of 13, 27, 87, 94 and 291 meV. The results of all methods were found to be in good agreement with each other. The consistency between the theoretical predictions for slow retrapping and experimental results showed that the retrapping process for the observed centers was negligible. The independence of peak position from concentration of carriers trapped in defect levels was also another indication of negligible retrapping. The dependence of TL glow curves on heating rate and distribution of traps was also studied.