In atomic force microscopy (AFM), a very sharp tip (cantilever) is scanned across the sample surface using piezoelectric scanners.

The measurement is monitored using the so called optical beam reflection detection system, in which a laser beam is reflected on the backside of the cantilever and onto a four quadrant position-sensitive photo sensor. This detector measures the bending of cantilever during the tip is scanned over the sample. The measured cantilever deflections are used to generate a map of the surface topography.

AFM can be used to study insulators and semiconductors as well as electrical conductors, biological samples, magnetic samples etc..

seeBerMad AFM and NATForce One AFM

AFM modes

Three imaging modes, contact mode, non-contact mode, and intermittent contact, can be used to produce topographic images of sample surfaces.

In contact mode, the tip makes "physical contact" with the sample, and is essentially dragged across the sample surface to make an topographic image. Contact mode imaging can be performed within a liquid environment, which essentially eliminates problems due to surface moisture such that much lower contact forces can be used.

In Non-contact mode the cantilever is vibrated near the surface of a sample. The spacing between the tip and the sample is on the order of tens to hundreds of angstroms. Like contact mode, the motion of the scanner is used to generate the topographic image.