Nitrogen atom diffusion into TiO2 anatase bulk via surfaces

Nitrogen atom diffusion from anatase surfaces to the bulk via the interstitial sites is studied by first principle calculations and nudged elastic band method. Anatase surfaces (1 0 1), (0 0 1), (1 0 0), and (1 0 3) are chosen for the surface diffusion calculations. It shows that the diffusion from the outermost surface to the sub-surface is the most difficult step for a N atom diffusing into the bulk and it is easier for a N atom diffusing out of the bulk and staying on the surface or at the sub-surface sites. According to the diffusion barriers, N diffusion into the bulk via a (1 0 1) surface is relatively easier than the diffusion via other three surfaces for the N doping process.