Dynamic behaviour of tuning fork shear-force feedback

A.G.T. Ruiter, J.A. Veerman, Kees van der Werf, N.F. van Hulst

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103 Citations (Scopus)


The dynamics of a tuning fork shear-force feedback system, used in a near-field scanning optical microscope, have been investigated, Experiments, measuring amplitude and phase of the tuning fork oscillation as a function of driving frequency and tip-sample distance, reveal that the resonance frequency of the tuning fork changes upon approaching the sample. Either amplitude or phase of the tuning fork can be used as distance control parameter in the feedback system. Using amplitude a second-order behavior is observed while with phase o­nly a first-order behavior is observed, and confirmed by numerical calculations. This first-order behavior results in an improved stability of our feedback system, A sample consisting of DNA strands o­n mica was imaged which showed a height of the DNA of 1.4 nm
Original languageUndefined
Pages (from-to)28-30
Number of pages3
JournalApplied physics letters
Issue number1
Publication statusPublished - 1997


  • METIS-128610
  • IR-23811

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