The Atomic Force Microscope (AFM)

This microscope, unlike its powerful predecessor the STM does not employ an electrical current between the tip and the specimen. In some modes of operation the tip actually makes contact with the specimen and may even be operated under liquid. Specimens which would be damaged by an electrical current can also been examined. Metal, mineral, organic material, macromolecules, insulators, plastics and ceramic material can all be examined using AFM.

An Atomic Force Microscope (AFM).

 

A close up view of the AFM specimen stage.

 

The operation of the AFM depends on the deflection of a cantilevered spring at the end of which there is a probe that is scanned across the surface of the specimen. The deflection of the spring is measured and provides the (Z) component of the topographical image. The scanned tip can detect a variety of different forces from a distance of about 1 nanometer above the surface. Amongst these are the weak Van der Waals, magnetic, electrostatic and capillary forces. When used in the contact mode ionic forces are the most important. The extremely small atomic forces between the specimen and the sharp tip of the probe cause deflections in the range of several micrometers to less than a tenth of a nanometer. These deflections are measured and used directly to construct a map of the specimen surface.