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Keywords:

  • Atomic Force Microscopy;
  • Acoustics;
  • Ultrasonic Waves

Abstract

Cantilevers of atomic force microscopes usually have spring constants of less than 1 N/m and fundamental resonance frequencies for free vibration between 10 and 100 kHz. If, however, the tip is in contact with the surface of a sample vibrating at MHz frequencies, we have observed that the cantilever can be forced to vibrate also at these high frequencies with high amplitude. For the detection of the high frequency vibrations of the cantilever we added in our experiment a fast optical knife-edge detector to a commercial Atomic Force Microscope. Ultrasonic pulses were excited by a piezoelectric transducer bonded to the sample and the ultrasonic signals transmitted to the cantilever were recorded. Furthermore, the vibrational amplitude of the cantilever was measured locally along the cantilever. For comparison we also measured the absolute surface amplitude by a Michelson-heterodyne interferometer. The spectral components of the cantilever vibration were examined and discussed theoretically.