Atom-resolved images of oxygen-deficient TiO2(110), obtained by scanning tunnelling microscopy and non-contact atomic force microscopy, were studied. Although scanning tunnelling microscopic images emphasized variations of Ti-atom density underneath the surface oxygen, non-contact atomic force microscopy images directly traced defect-induced structures of top-most oxygen atoms. It was first found that the (1x3) phases were not composed of missing TiO2 units, but added Ti2O3 rows. The deformed (1x3) phase was observed by half steps along [001], which well explained that diffusion and adsorption of segregated impurities helped in the formation of (1x3) phases.

STM and Atomic-Resolution Non-Contact AFM of an Oxygen-Deficient TiO2 (110) Surface. Ashino, M., Uchihashi, T., Yokoyama, K., Sugawara, Y., Morita, S., Ishikawa, M.: Physical Review B, 2000, 61[20], 13955-9