Effect of thermal heat treatment on oxygen-deficiency-associated defect centers: Relation to 1.8 eV photoluminescence bands in silica glass

Our previous studies have reported the existence of a 1.8 eV photoluminescence (PL) band [full width at half-maximum (FWHM) of 0.2–0.4 eV, decay time τ of ∼200 ns, PL excitation peak of 2.1 eV] in silica glass exposed to visible light. Oxygen-deficiency-associated defect centers [Si clusters or SiOx (x<2) structure] were thought to be the origin of this PL band. In this article, we describe the thermal heat treatment characteristics of the 1.8 eV PL band in silica glass (excited by visible light). In the low-temperature region (∼600 °C), we observed a decrease in the intensity of this PL band. On the other hand, the 2.1 eV PL band (FWHM of ∼0.32 eV, τ unknown) was observed for the case of annealing at a temperature around 1050 °C. We propose that the high probability SiOx (x<2) structure rather than the Si clusters plays a predominant role in the generation of the 1.8 eV PL band, and that crystalline Si nanoparticles are probably the origin of the 2.1 eV PL band.