Non-contact atomic force microscopy imaging of the TiO2 (110) surface was simulated by using first-principles and atomistic methods. Three different tip models were used to investigate the tip-surface interaction on the ideal surface, and agreement with experiment was found for either a Si tip or a tip with a net positive electrostatic potential from the apex. Both predicted bright contrast over the bridging O rows. A study was then made of the interaction of this tip with a bridging O vacancy on the surface, and it was found that the much weaker interaction observed would result in vacancies appearing as dark contrast along the bright rows in images.

Simulating Atomic Force Microscopy Imaging of the Ideal and Defected TiO2 (110) Surface. Foster, A.S., Pakarinen, O.H., Airaksinen, J.M., Gale, J.D., Nieminen, R.M.: Physical Review B, 2003, 68[19], 195410