Tip-sample interactions in scanning force microscopy using the frequency-modulation technique: Experiments and computer simulation

Abstract

The resonance frequency and the damping behaviour of a vibrating cantilever as used in dynamic Scanning Force Microscopy (SFM) is investigated with the frequency modulation (FM) technique. The properties of a silicon-cantilever/tip vibrating in front of a silicon surface were studied under UHV conditions as a function of the tip-sample distance. The experimental results are compared with a computer simulation. The different characteristic parts of the experimental curves can be interpreted in terms of attractive and repulsive forces acting on the cantilever as well as the behaviour of the amplitude control electronics. Using the computer simulation noncontact regimes can clearly be distinguished from intermittent contact regimes.

Image simulation of a corrugated surface in the constant-force-gradient mode of the scanning force microscope

“…We have studied the influence of the tip's shape on the images in the constant-height and the dynamic non-contact modes. Small nanostructures may be detected for both tip shapes in both modes, in an UHV experiment during which the noise would be kept at a low level [14]. These conditions appear very critical in the constant-height mode because the forces are weak, but they are not crucial in the resonant or the constant-force-gradient mode, which is similar to the dynamic scanning force microscopy [34].…”

“…Another point is that a time-resolved simulation of the dynamical mode could be performed with the present model, by including the three-dimensional force calculated with our model in a Verlet algorithm. It would allow one to go beyond the one-dimensional harmonic modelling of the cantilever oscillations [14].…”

“…The spatial resolution of this mode is studied as a function of the separation between the nanostructures. In section 4, using a numerical feedback loop, we simulate the constant-forcegradient mode in which the force gradient between the tip and the sample is experimentally measured through the changes in the vibration amplitude of the cantilever supporting the probe or through the changes in resonance frequency [14]. Here too, we discuss the resolution factor and the influence of the chemical nature of the substrate on the nanostructures' apparent height, after having proposed a definition of this quantity.…”

Brownian Force Profile Reconstruction of Interfacial 1-Nonanol Solvent Structure

“…The methods for directly measuring force profiles and energy landscapes can initially be split into two technique categories: oscillatory and static deflection. Oscillatory techniques, such as force modulation atomic force microscopy (FMAFM), drive the probe near the sample in the spring's harmonic potential and use the phase, amplitude, and oscillation frequency to determine the potential. − Frequency detection is more accurate in a low damping environment, causing the implementation of FMAFM to be very difficult in solution, where the majority of interesting samples are investigated. Static deflection techniques measure spring deflection at low frequencies and use Hooke's law to calculate force.…”