Topographic and electronic contrast of the graphene moir\'e on Ir(111) probed by scanning tunneling microscopy and non-contact atomic force microscopy

Epitaxial graphene grown on transition metal surfaces typically exhibits a moir\'e pattern due to the lattice mismatch between graphene and the underlying metal surface. We use both scanning tunneling microscopy (STM) and atomic force microscopy (AFM) experiments to probe the electronic and topographic contrast of the graphene moir\'e on the Ir(111) surface. While STM topography is influenced by the local density of states close to the Fermi energy and the local tunneling barrier height, AFM is capable of yielding the 'true' surface topography once the background force arising from the van der Waals (vdW) interaction between the tip and the substrate is taken into account. We observe a moir\'e corrugation of 35$\pm$10 pm, where the graphene-Ir(111) distance is the smallest in the areas where the graphene honeycomb is atop the underlying iridium atoms and larger on the fcc or hcp threefold hollow sites.Comment: revised versio

Intermolecular Contrast in Atomic Force Microscopy Images without Intermolecular Bonds

Intermolecular features in atomic force microscopy images of organic molecules have been ascribed to intermolecular bonds. A recent theoretical study [P. Hapala et al., Phys. Rev. B 90, 085421 (2014)] showed that these features can also be explained by the flexibility of molecule-terminated tips. We probe this effect by carrying out atomic force microscopy experiments on a model system that contains regions where intermolecular bonds should and should not exist between close-by molecules. Intermolecular features are observed in both regions, demonstrating that intermolecular contrast cannot be directly interpreted as intermolecular bonds

Intermolecular Contrast in Atomic Force Microscopy Images without Intermolecular Bonds

Intermolecular features in atomic force microscopy images of organic molecules have been ascribed to intermolecular bonds. A recent theoretical study [P. Hapala et al., Phys. Rev. B 90, 085421 (2014)] showed that these features can also be explained by the flexibility of molecule-terminated tips. We probe this effect by carrying out atomic force microscopy experiments on a model system that contains regions where intermolecular bonds should and should not exist between close-by molecules. Intermolecular features are observed in both regions, demonstrating that intermolecular contrast cannot be directly interpreted as intermolecular bonds

Characterization of a Hexagonal Phosphorus Adlayer on Platinum (111)

| openaire: EC/FP7/610446/EU//PAMSPeer reviewe

Many-body transitions in a single molecule visualized by scanning tunnelling microscopy

Many-body effects arise from the collective behaviour of large numbers of interacting particles, for example, electrons, and the properties of such a system cannot be understood considering only single or non-interacting particles1–5. Despite the generality of the many-body picture, there are only a few examples of experimentally observing such effects in molecular systems6–8. Measurements of the local density of states of single molecules by scanning tunnelling spectroscopy is usually interpreted in terms of single-particle molecular orbitals9–11. Here, we show that the simple single-particle picture fails qualitatively to account for the resonances in the tunnelling spectra of different charge states of cobalt phthalocyanine molecules. Instead, these resonances can be understood as a series of many-body excitations of the different ground states of the molecule. Our theoretical approach opens an accessible route beyond the single-particle picture in quantifying many-body states in molecules