Quantifying amplitude reduction in tapping mode atomic force microscopy
conference paper
In this paper the research question is why the amplitude reduces when the tip interacts with sample in Tapping Mode Atomic Force Microscopy (TMAFM)? This question has already been answered in the late 1990’s briefly: “The amplitude reduces because the resonance frequency of the system changes”. The explanation arises from a nonlinear dynamics study of the cantilever in presence of nonlinear Hertzian contact and van der Waals forces and contains no restrictive assumptions. However, some behavior of AFM cantilever in tapping mode can hardly be explained with the existing theory. For example, we have observed that the tip-sample interaction forces in TM-AFM are very sensitive to the excitation frequency. Two different excitation frequencies; one higher, and one lower than the resonance frequency apply very different forces on the sample. This holds even if the excitation voltage, free air amplitude, and amplitude set-point are the same for both frequencies. As shown in Fig.1a, the maximum of interaction force, i.e. the Peak Repulsive Force (PRF), have a saddle shape trend with respect to amplitude ratio and normalized excitation frequency. In Fig.1b we experimentally confirm this observation and we introduce a mask-less patterning technique by tuning the tip-sample forces via the excitation frequency.
TNO Identifier
1019035
Source title
13th International Workshop on Nanomechanical Sensing, NMC 2016, Delft, The Netherlands
Collation
2 p.
Files
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