Probe-surface interaction in near-field optical microscopy: The nonlinear bending force mechanism

Abstract

The probe-surface interaction underlying the ‘‘shear-force’’ distance control commonly used in near-field microscopy has been studied in detail by measuring dither resonance profiles and approach curves in vacuum and liquid helium. Simulations based on a nonlinear oscillator model considering the probe geometry, its elastic properties, adiabatic short-range probe-surface contact, and the surface tilt angle, are in excellent agreement with the experiments. We prove conclusively that a nonlinear bending force mechanism with parametric mode conversion is responsible for the observed phenomena.

Friction and Molecular Deformation in the Tensile Regime

“…It should be noted that the attractive displacement range is independent of the initial free amplitude of the tip's lateral motion for free amplitudes #12 nm. Thus we do not attribute the attractive/tensile interaction range to a slight tilt of the tip with respect to the samples [20].…”

Scanning near-field optical microscopy with aperture probes: Fundamentals and applications

“…The origin of the shear force effect is not entirely clear. There might be a range of mechanism involved, including viscous damping in thin water films, 47,48 intermittent contact, 49 and electrostatic image forces. 50 The phase signal reacts faster to changes in the state of oscillation, because it is independent of the dissipation of kinetic energy stored in the resonance.…”

Tuning fork shear-force feedback

“…Several possible interaction mechanisms have been proposed as an explanation, e.g. capillary forces [2], van der Waals forces and actual contact between fiber and sample [8]. In this paper the effect of this interaction on the amplitude and phase of the oscillation of the tuning fork will be discussed and the consequences for the dynamics of a feedback mechanism acting on either one of these signals will be demonstrated.…”