Optical Properties of Complex Anion Vacancy Centres and Photo-Excited Electronic Processes in Anion Defective Alpha-Al2O3

Abstract

A comparative investigation of the optical characteristics and nature of electronic processes in a-Al₂O₃ crystals was carried out for thermal treatments involving a quenching or an annealing procedure. The formation of a defect with stimulation band at 4.11 eV and two luminescence bands at 2.5 eV and 3.82 eV during annealing has been observed. Results support the F₂ centre as a probable model for this defect. Excitation in the absorption band of the F₂ centre at 4.11 eV at RT results both in intrinsic luminescence at 3.82 eV and 2.5 eV as well as in photo-ionisation of the F₂ centre. The F₂ centre takes part in the phototransfer of electrons and acts as a recombination centre in TSL. The presence of F₂ centres in crystals may considerably affect the dosimetric characteristics of the anion defective a-Al₂O₃.