In this study we simulate noncontact atomic force microscopy imaging of the TiO2 (110) surface using first-principles and atomistic methods. We use three different tip models to investigate the tip-surface interaction on the ideal surface, and find that agreement with experiment is found for either a silicon tip or a tip with a net positive electrostatic potential from the apex. Both predict bright contrast over the bridging oxygen rows. We then study the interaction of this tip with a bridging oxygen vacancy on the surface, and find that the much weaker interaction observed would result in vacancies appearing as dark contrast along the bright rows in images.
Foster, A. S., Pakarinen, O. H., Airaksinen, J. M., Gale, J. D., & Nieminen, R. M. (2003). Simulating atomic force microscopy imaging of the ideal and defected TiO2 (110) surface. Physical Review B, 68(19), 1-8. . https://doi.org/10.1103/PhysRevB.68.195410