Force Modulation Microscopy (FMM)

In Force Modulation Microscopy (FMM), the cantilever is oscillated while it is scanned across the sample surface. The oscillation amplitude of the cantilever changes depending on the local hardness of the surface, which is reflected in the PSPD signal. The amplitude change of the PSPD signal, which is used to calculate surface hardness, is extracted by an internal lock-in amplifier.