'All-inclusive' imaging of the rutile TiO2(110) surface using NC-AFM

Non-contact atomic force microscopy (NC-AFM) at true atomic resolution is used to investigate the (110) surface of rutile TiO2. We are able to simultaneously resolve both bridging oxygen and titanium atoms of this prototypical oxide surface. Furthermore, the characteristic defect species, i.e. bridging oxygen vacancies, single and double hydroxyls as well as subsurface defects, are identified in the very same frame. We employ density functional theory (DFT) calculations to obtain a comprehensive understanding of the relation between the tip apex structure and the observed image contrast. Our results provide insight into the physical mechanisms behind atomic-scale contrast, indicating that electrostatic interaction can lead to a far more complex contrast than commonly assumed.