Noncrystalline SiO2 and GeO2: Process Induced Pre-existing Defects and Vacated O-atom Intrinsic Bonding Sites

Electron spin resonance (ESR) studies on bulk-quenched, noncrystalline (nc-) silica glasses (henceforth, nc-SiO2) have distinguished between (1) pre-existing process-induced defects introduced either after growth or annealing at high temperatures and (2) x-ray or γ-ray radiation or energetic electron particle-created defects. The ESR activity in these pre-existing defects is activated by x-rays. Similar pre-exiting defects have been demonstrated for remote plasma-deposited thin films of nc-SiO2 and nc-GeO2. Concentrations of pre-existing defects increase exponentially with increasing quenching and annealing temperatures. This is always the case for so-called “dry silicas” with no detectable Si–OH bonding. Nonbonding O-hole centers or nonbonding O-associated hole centers are also detected in dry silicas but only after significant x-ray, γ-ray, or energetic electron irradiation. Pre-existing defect has also been detected by second derivative O K pre-edge x-ray absorption spectroscopy in thermally grown and ...