Atomic force microscopy

Atomic Force Microscopy (AFM) is a technique closely related to Scanning Tunneling Microscopy. The AFM probes the surface of a sample using a sharp diamond tip, a couple of microns long and less than 100 Angstroms in diameter. The tip is located at the end of a cantilever, which is about 100-200 microns long. Forces between the sample and the tip result in bending or deflections of the cantilever. The cantilever deflections can be measured using laser light deflection on the cantilever beam.

Several forces can be measured by the deflection of the AFM cantilever. The AFM can be operated in contact mode; in this mode, the tip makes soft physical contact with the surface. The AFM can also be operated in non-contact mode. In non-contact mode, the cantilever is held less than a few angstroms above the sample surface, and van der Waals forces can be measured.

Using AFM, surfaces of a wide variety of materials can be analyzed on an atomic level. The AFM is used for the analysis of insulators, semiconductors, and electrical conductors.

By changing the detector the laser beam strikes from two photodiodes to four arranged in a square, the microscope can also detect twisting of the cantilever.

This means the microscope will be sensitive to sideways forces. Lateral force microscopy is used for tribology at very fine resolutions.