Influence of ultrasonic surface acoustic waves on local friction studied by lateral force microscopy

We studied dynamic friction phenomena introduced by ultrasonic surface acou stic waves using a scanning force microscope in the lateral force mode and a scanning acoustic force microscope. An effect of friction reduction was f ound when applying surface acoustic waves to the micromechanical tip-sample contact. Employing standing acoustic wave fields, the wave amplitude depen dent friction variation can be visualized within a microscopic area. At hig her wave amplitudes, a regime was found where friction vanishes completely. This behavior is explained by the mechanical diode effect, where the tip's rest position is shifted away from the surface in response to ultrasonic w aves.