Density functional calculations using model clusters were performed to clarify the atomic-scale diffusion mechanism of an O2 molecule or an O atom in SiO2. The activation energy required for the atomic O diffusion was estimated to be 1.3eV, whereas that for the molecular O2 diffusion was revealed to be fairly low, 0.3eV. This strongly suggested that the diffusing O in SiO2 was primarily in a molecular form. The computational results were confirmed to be consistent between two SiO2 configurations of the cristobalite and quartz structures. Diffusion pathways and the related activation energies were shown to be well compatible with many recent works.

Diffusion of Molecular and Atomic Oxygen in Silicon Oxide. T.Hoshino, M.Hata, S.Neya, Y.Nishioka, T.Watanabe, K.Tatsumura, I.Ohdomari: Japanese Journal of Applied Physics-1, 2003, 42[6A], 3560-5