Role of Mobile Interstitial Oxygen Atoms in Defect Processes in Oxides: Interconversion between Oxygen-Associated Defects in ${\mathrm{S}\mathrm{i}\mathrm{O}}_2$ Glass

The role of mobile interstitial oxygen atoms (${\mathrm{O}}^0$) in defect processes in oxides is demonstrated by interconversion between the oxygen dangling bond and the peroxy radical (POR) in ${\mathrm{S}\mathrm{i}\mathrm{O}}_2$ glass. Superstoichiometric ${\mathrm{O}}^0$ was created by ${\mathrm{F}}_2$ laser photolysis of the interstitial ${\mathrm{O}}_2$. On annealing above $300°\mathrm{C}$, ${\mathrm{O}}^0$ migrated and converted the oxygen dangling bond to POR. Exposure to 5.0 eV light converted POR back to a pair of the oxygen dangling bond and ${\mathrm{O}}^0$ (quantum yield: $\sim 0.1$). These findings suggest that various defect processes typically occurring in ${\mathrm{S}\mathrm{i}\mathrm{O}}_2$ glass at $\sim 300–500°\mathrm{C}$ are related to migration of ${\mathrm{O}}^0$, which exists in the glass network in the peroxy linkage form.

Figure 1

Concentration changes of the $E^{\prime }$ center, NBOHC, POR, and interstitial ${\mathrm{O}}_2$ in the ${\mathrm{F}}_2$-laser-irradiated (a) low-${\mathrm{O}}_2$ and (b) high-${\mathrm{O}}_2$ samples on isochronal anneals for 10 min at each temperature. In the high-${\mathrm{O}}_2$ sample, the dotted line indicates the ${\mathrm{O}}_2$ concentration before the irradiation.

Figure 2

Concentration changes of the $E^{\prime }$ center, NBOHC, POR, and interstitial ${\mathrm{O}}_2$ in the ${\mathrm{F}}_2$-laser-irradiated high-${\mathrm{O}}_2$ sample during multiple cycles of thermal anneal (30 min at $500°\mathrm{C}$) and subsequent brief exposure to KrF laser light at ambient temperature (600 pulses of $\sim 100\mathrm{m}\mathrm{J}{\mathrm{c}\mathrm{m}}^{-2}{\mathrm{\text{pulse}}}^{-1}$). The dotted line indicates the ${\mathrm{O}}_2$ concentration before the ${\mathrm{F}}_2$ laser irradiation.

Figure 3

Normalized concentration change of POR versus number of KrF laser pulses recorded at different pulse energies for the high-${\mathrm{O}}_2$ sample which has been ${\mathrm{F}}_2$ laser irradiated and thermally annealed for 30 min at $500°\mathrm{C}$. The dotted line indicates the POR concentration before the thermal anneal. The inset shows the rates of concentration change of NBOHC and POR as a function of the pulse energy. They were calculated assuming that the concentration change follows a single exponential.