Atomic force microscopy

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

AMF schematic

The sample is placed on an x-y piezo stage. A cantiliever with a sharp tip is approaching to the surface. A laser beam is focused on the cantiliever and reflected into a photodiode detector. Position of the laser spot on the photodiode enables monitoring deflection of cantiliever’s deflection, amplitude of its vibration or shift in the resonant frequency. Thus, detector controls motion of the cantiliever into 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