An experimental and theoretical investigation was made of the atomically resolved distribution of excess charge created by a single oxygen atom vacancy and an hydroxyl impurity defect on rutile (110) surfaces. Contrary to the conventional model, where the charge remained localized at the defect, scanning tunnelling microscopy and density functional theory here showed it to be delocalized over multiple surrounding titanium atoms.

The Electronic Structure of Oxygen Atom Vacancy and Hydroxyl Impurity Defects on Titanium Dioxide (110) Surface. Minato, T., Sainoo, Y., Kim, Y., Kato, H.S., Aika, K., Kawai, M., Zhao, J., Petek, H., Huang, T., He, W., Wang, B., Wang, Z., Zhao, Y., Yang, J., Hou, J.G.: Journal of Chemical Physics, 2009, 130[12], 124502