OPTICAL-PROPERTIES OF COMPLEX ANION VACANCY CENTERS AND PHOTO-EXCITEDELECTRONIC PROCESSES IN ANION DEFECTIVE ALPHA-AL2O3

A comparative investigation of the optical characteristics and nature of electronic processes in alpha-Al2O3 crystals was carried out for th ermal treatments involving a quenching or an annealing procedure. The formation of a defect with stimulation band at 4.11 eV and two lumines cence bands at 2.5 eV and 3.82 eV during annealing has been observed. Results support the F-2 centre as a probable model for this defect. Ex citation in the absorption band of the F-2 centre at 4.11 eV at RT res ults both in intrinsic luminescence at 3.82 eV and 2.5 eV as well as i n photo-ionisation of the F-2 centre. The F-2 centre takes part in the phototransfer of electrons and acts as a recombination centre in TSL. The presence of F-2 centres in crystals may considerably affect the d osimetric characteristics of the anion defective alpha-Al2O3.