Atomic force microscopy

Jul 12, 2022

Atomic force microscopy (AFM) is a type of scanning probe microscopy that is designed to probe surface topography at high spatial resolution. The scheme below shows the basic principle of AFM.

AMF schematic

The sample is placed on an x-y piezo stage. A cantilever with a sharp tip is approaching the surface. A laser beam is focused on the cantilever and reflected into a photodiode detector. The position of the laser spot on the photodiode enables monitoring the cantilever’s deflection, the amplitude of its vibration, or the shift in its resonant frequency. Thus, the detector converts the cantilever’s motion into an electrical signal processed by the control unit. From the obtained signal, the software can reconstruct the surface topography on the scanning area. Various modes of AFM operation exist, including contact, tapping, and non-contact modes.

The figure below shows examples of the surface topography obtained using the AFM.

AMF schematic

References