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.

The effective electron affinity estimation from the simultaneous detection of thermally stimulated luminescence and exoelectronic emission. Application to an -alumina single crystal

“…We agree with this hypothesis for exoelectrons observed at about 230 K [5], which correspond to hole detrapping [5,6,8,9], and for the thermally stimulated peaks at about 60 K [10] and 100 K [5], which are also related to the release of holes [9]. Nevertheless, the case of the 275 K TSEE peak is quite different: this peak is due to electron detrapping [5,6,9] and could be explained by the direct ejection of electrons into the vacuum [5]. The same assumption could be made for peak 440 K which is also due to electron detrapping [8].…”

“…Most of the works [6,7] devoted to the study of the TSEE mechanisms of α-alumina conclude that TSEE is governed by an Auger-like mechanism. We agree with this hypothesis for exoelectrons observed at about 230 K [5], which correspond to hole detrapping [5,6,8,9], and for the thermally stimulated peaks at about 60 K [10] and 100 K [5], which are also related to the release of holes [9]. Nevertheless, the case of the 275 K TSEE peak is quite different: this peak is due to electron detrapping [5,6,9] and could be explained by the direct ejection of electrons into the vacuum [5].…”

“…The emission spectra of α-alumina TL peaks often reveal the existence of two components at 320 and 410 nm [8,9] which are interpreted as the result of the recombination of a hole (e + ) with an F centre or of an electron (e − ) with an F + centre respectively:…”

Thermoluminescence of Al2O3 crystals grown by temperature gradient techniques

“…Cook et al [7] studied low-temperature TL (ltTL) of Al 2 O 3 in the range 10 to 300 K, using X-ray and UV irradiation, and observed 60 K (E=0.17 eV), 100 K (E=0.22 eV), and 220 K (E=0.56 eV) peaks that arise from thermal release of trapped holes from F-type centers. In addition, 260 K (E=0.72 eV) and 290 K peaks attributed to thermal-released electrons from F + -type centers are also observed.…”

“…Much work [6][7][8][9] has been done to study the TL properties of Al 2 O 3 crystals in the range 90-500 K. These studies have shown that TL peaks at 60, 100, 220, 260, and 290 K were associated with F-type centers and 435 K peak was attributed to V-type centers. Little work has been done though on the TL properties of Al 2 O 3 crystals grown in a reducing atmosphere.…”