Diffusion of oxygen molecules in fluorine-doped amorphous SiO2

Effects of fluorine doping on the diffusion of interstitial oxygen molecules (O₂) in amorphous SiO₂ (a-SiO₂) were compared to those obtained from a-SiO₂ containing SiOH groups. Incorporation of moderate concentration (∼1019 cm^-3) of SiF groups gives rise to minor changes in diffusion parameters between 800 and 1100 °C: only a slight decrease in solubility and an increase in the activation energy for diffusion can be detected. Incorporation of SiOH groups has similar weak effects on the solubility and activation energy for diffusion. These minor changes are most likely due to the enhancement of the flexibility of local Si-O network as a result of the dissociation of the network by SiOH and SiF groups. However, in contrast to the SiF doping, SiOH doping leads to a notable decrease in the diffusion coefficient. The heat of solution changes by ∼0.1-0.2 eV at ∼1000 ° C and it is attributed to the glass transition of a-SiO ₂.