Atomic force microscopy calibration of standing surface acoustic wave amplitudes

TL;DR

This paper introduces a calibration method for surface acoustic wave amplitudes using atomic force microscopy, addressing inaccuracies caused by cantilever deflection exceeding actual wave amplitudes at high frequencies.

Contribution

A novel calibration technique based on force-curve measurements and cantilever motion equations for high-frequency surface acoustic waves.

Findings

Calibration method validated on GaAs crystal at 3 GHz

Cantilever deflection can overestimate surface wave amplitude

Improved accuracy in high-frequency surface acoustic wave measurements

Abstract

Atomic force microscopy is an important tool for characterizing surface acoustic waves, in particular for high frequencies, where the wavelength is too short to be resolved by laser interferometry. A caveat is, that the cantilever deflection is not equal to the amplitude of the surface acoustic wave. We show, that the energy transfer from the moving surface to the cantilever instead leads to a deflection exceeding the surface modulation. We present a method for an accurate calibration of surface acoustic wave amplitudes based on comparing force-curve measurements with the equation of motion of a driven cantilever. We demonstrate our method for a standing surface acoustic wave on a GaAs crystal confined in a focusing cavity with a resonance frequency near 3 GHz.