Dopant induced surface reconstruction in N-doped rutile TiO$_{2}$(110)

Recently N-doping of TiO$_{2}$ has attracted some attention because it has been demonstrated to shift the photocatalytic activity of TiO$_{2}$ from the UV-region to the visible light. Here we examine the impact of N-doping on the electronic structure and surface morphology of single crystal TiO$_{2}$ surfaces.* Often it is assumed that bulk dopants have little influence on the surface properties. In the case of rutile TiO$_{2}$(110) it is, however, well established that intrinsic O-vacancies cause the surface to reconstruct to form a 1x2 superstructure. We find that N-doping reduces the formation energy of O-vacancies in TiO$_{2}$ and as a consequence destabilizes the surface to cause a 1x2 reconstruction. Similar surface effects may be expected for other bulk dopants that are know to induce oxygen vacancies in TiO$_{2}$. * M. Batzill, E.H. Morales, U. Diebold, Phys. Rev. Lett. accepted