Diffusion of molecular and atomic oxygen in silicon oxide

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 O diffusion was estimated to be 1.3 eV, whereas that for the molecular O₂ diffusion was revealed to be fairly low, 0.3 eV. This strongly suggests that the diffusing oxygen in SiO₂ is primarily in a molecular form. The computational results were confirmed to be consistent between two SiO₂ configurations of the cristobalit and quartz structures. Diffusion pathways and the related activation energies are shown to be well compatible with many recent works.