Low-temperature thermoluminescence studies of Al23

Abstract

Thermoluminescence (TL) and emission spectra studies of single-crystal A1203 have been conducted in the temperature interval 10-300 K. Glow curves resulting from either x or UV radiation at 10 K were recorded and analyzed to yield thermal activation energies (E) and frequency factors (s) associated with each glow peak. A typical glow curve exhibits maxima at 60 K (E = 0.17 eV, s = 5×1012 s−1), 100 K (E = 0.22 eV, s = 8×109 s−1), 220 K (E = 0.56 eV, s = 7×1010 s−1), 260 K (E = 0.72 eV, s = 3×1012 s−1), and 290 K (E and s could not be deduced). Spectral emission from these peaks are characterized by predominant bands centered near either 330 or 410 nm. Specifically, the TL peaks at 60, 100, 220 K exhibit the band near 330 nm, whereas the 260- and 290-K peaks display the 410-nm band. Thermal annealing, optical excitation, and photobleaching experiments were also conducted in efforts to deduce the recombination mechanisms responsible for the glow peaks. Experimental results suggest that the 60-, 100-, and 220-K peaks are due to the thermal release of trapped holes which recombine with electrons of the F centers producing F+ centers in an excited state. De-excitation of these centers produces 330-nm radiation. Moreover, the 260- and 290-K peaks are attributed to the thermal release of trapped electrons that recombine with existing F+ centers converting them to excited-state F centers, which relax to the ground state and produce 410-nm radiation.