title: Spectroscopy of the shear force interaction in scanning near-field optical microscopy.
abstract: Shear force detection is a common method of tip-sample distance control in scanning near-field optical microscopy. Shear force is the force acting on a laterally oscillating probe tip near a surface. Despite its frequent use, the nature of the interaction between tip and sample surface is a matter of debate. In order to investigate the problem, approach curves, i.e. amplitude and phase of the tip oscillation as a function of the tip-sample distance, are studied in terms of a harmonic oscillator model. The extracted force and damping constants are influenced by the substrate material. The character of the interaction ranges from elastic to dissipative. The interaction range is of atomic dimensions with a sharp onset. Between a metal-coated tip and a Cu sample, a power law for the force-distance curve is observed.
authors.affiliation: Freie Universität Berlin, Institut für Experimentalphysik, Arnimallee 14, 14195 Berlin, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Hoppe
authors.forename: Georgios
authors.initials: G
authors.lastname: Ctistis
authors.forename: Jens J
authors.initials: JJ
authors.lastname: Paggel
authors.forename: Paul
authors.initials: P
authors.lastname: Fumagalli
mesh_terms: D018625:Microscopy, Atomic Force; D008962:Models, Theoretical; D013057:Spectrum Analysis; D013314:Stress, Mechanical; D014732:Vibration