Point defects related to 260 K thermostimulated luminescence in α-Al2O3

Abstract

Thermo- and photostimulated processes are studied in reduced hydrogen containing α-Al 2 O 3 excited by UV light. It is found that UV excitation in F absorption band at 90 K results in a ionization of the F-centers and capture of released electrons at defects thus producing an anisotropy absorption band at 4.2 eV and the dominant thermoluminescence (TL) peak at 260 K. The 260 K TSL peak is accompanied by complete bleaching of the 4.2 eV absorption band and vice versa-by light stimulation in the region of the 4.2 eV band the 260 K TSL peak disappear and released electrons recombine with F + -centers. Both the effect of the preliminary high-temperature thermal treatment of samples on formation of 4.2 eV-centers and the observed dichroism characteristics allows to conclude that corresponding complex defect contains hydrogen and can involve vacancy pair.