REACTIONS OF HYDROGENATED DEFECTS IN FUSED-SILICA CAUSED BY THERMAL-TREATMENT AND DEEP ULTRAVIOLET-IRRADIATION

Nuclear magnetic resonance (NMR) was used to study hydrogen in fused silica for the first time. The H-1 NMR spin-lattice relaxation time constant (T1) in synthetic fused silica was found to be strongly affected by thermal treatments, correlating with the concentration of E' centers produced during subsequent 193-nm excimer-laser irradiation. In addition, the relative proportion of the two components in the NMR spectrum were affected by thermal treatment, although no change in the total hydrogen content was observed. The broad NMR component, because of its linewidth and dependence upon thermal processing, is postulated to be a direct signature of the NMR relaxation centers. These results are interpreted within the framework of a model in which pairs of silanol groups are consumed during thermal treatment, forming a strained bond which is susceptible to E' center formation.