Formation and decay of nonbridging oxygen hole centers in SiO2 glasses induced by F2 laser irradiation: In situ observation using a pump and probe technique

Formation and decay of nonbridging oxygen hole centers (NBOHC, an oxygen dangling bond) in SiO2 glasses by F2 excimer laser (7.9 eV) irradiation were in situ analyzed by monitoring 1.9 eV photoluminescence of NBOHC using a pump and probe technique. In wet SiO2, the SiO–H bond was efficiently photolyzed by F2 laser photons to form NBOHC with a quantum yield of ∼0.2. However, the recombination with dissociated hydrogenous species suppressed the buildup of NBOHC. In dry SiO2, in contrast, NBOHC formation by dissociation of strained Si–O–Si bonds was inefficient but NBOHC accumulated with the number of F2 pulses due to a negligibly slow reverse recombination reaction.