A comparative experimental study on sample excitation and probe excitation in force modulation atomic force microscopy

Probe dynamics and imaging characteristics of force modulation atomic force microscopy (FMM) with either sample excitation or probe excitation were investigated and compared experimentally. In both acoustic excitation methods, the contact resonance frequency of the probe is usually masked by spurious frequency peaks, which may cause difficulties in accurate identification. Two approaches can help to determine the exact contact resonance. One is by comparing the dynamic spectra obtained at the cantilever end and at a slight detection position offset. The other is by comparing the frequency spectra via these two different excitations. Generally, the sample excitation and the probe excitation produce similar FMM images except when driving at or near the spurious frequencies. In both excitation methods, the cross-talk of the surface geometry in FMM data is obvious, which may distort the measurements of local mechanical properties.