title: Forces and currents in carbon nanostructures: are we imaging atoms?
abstract: First-principles calculations show that the rich variety of image patterns found in carbon nanostructures with the atomic force and scanning tunneling microscopes can be rationalized in terms of the chemical reactivity of the tip and the distance range explored in the experiments. For weakly reactive tips, the Pauli repulsion dominates the atomic contrast and force maxima are expected on low electronic density positions as the hollow site. With reactive tips, the interaction is strong enough to change locally the hybridization of the carbon atoms, making it possible to observe atomic resolution in both the attractive and the repulsive regime although with inverted contrast. Regarding STM images, we show that in the near-contact regime, due to current saturation, bright spots correspond to hollow positions instead of atomic sites, providing an explanation for the most common hexagonal pattern found in the experiments.
authors.affiliation: Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 162 00, Prague, Czech Republic.
authors.forename: Martin
authors.initials: M
authors.lastname: Ondráček
authors.forename: Pablo
authors.initials: P
authors.lastname: Pou
authors.forename: Vít
authors.initials: V
authors.lastname: Rozsíval
authors.forename: Cesar
authors.initials: C
authors.lastname: González
authors.forename: Pavel
authors.initials: P
authors.lastname: Jelínek
authors.forename: Rubén
authors.initials: R
authors.lastname: Pérez