Resolving the adsorption of molecular O 2 on the rutile TiO 2 (110) surface by noncontact atomic force microscopy

Significance MolecularO 2 on semiconducting metal oxides, its adsorption, response to thermal treatment, UV irradiation, and electron/hole injection is at the heart of a wide range of technologies. These processes were studied molecule by molecule on the prototypical model oxideT i O 2 (110), using noncontact AFM. We show that the nonintrusive nature of the nc-AFM and its exceptional spatial resolution due to the functionalization of the tip with a terminal O atom allow identifying oxygen adsorption geometries which were not previously determined by other techniques. In combination with density functional theory calculations, we explain the charge states of the various adsorbed oxygen species, their dynamics upon annealing and UV irradiation, and the role of electron exchange with theT i O 2 substrate.