Subsurface depth dependence of nitrogen doping in TiOanatase: a DFT study.

We report first-principles calculations of the structure and electronic structure of nitrogen-doped TiOanatase as a function of the dopant depth below the (101) surface. Specifically we evaluate the depth dependence of the formation energy for a few positions of the N impurity, considering for both substitutional and interstitial sites. We find a significant advantage of interstitial over substitutional positions, and a mild dependence of this formation energy on depth.