The first atomic force microscope (AFM) was invented by Binning, Quate and Gerber in 1986. Unlike scanning tunnelling microscopy, AFM can be used to examine both conducting and non-conducting surfaces. The spatial resolution of an atomic force microscope depends on the size of the cantilever and the curvature of its tip. AFMs demonstrate horizontal distance resolution on the order of an atom size and an even higher vertical distance resolution. Interaction is generally understood as attractive interaction between the probe and the surface caused by van der Waals forces and repulsive interaction caused by electrostatic forces (a wide range of the method's modifications exist that are used to analyse other interactions, such as electrostatic, magnetic, friction forces, etc.). When the tip is far enough from the specimen, the attraction force between the probe and the surface is week. As the distance decreases, the force grows until electrostatic repulsion occurs in the electron clouds of the tip and the surface. The attraction and repulsion forces equalize when the distance between the tip and the surface equals the bond distance (several dozen nm); repulsion will prevail in the case of smaller distances.

The distance from the probe tip to the surface defines the specific AFM mode, which can be one of the following:

-contact mode;

-non-contact mode;

-tapping mode.

In contact mode, the distance between the tip and the specimen is in the order of several dozen nanometres. The AFM probe tip is in soft physical contact with the specimen and is subject to repulsion forces.

Interaction between the tip and the specimen causes the cantilever to flex, thus reproducing the surface topography. Topographic images are usually obtained in AFM in one of two modes: constant height mode or constant force mode.

In non-contact mode (attraction mode), a piezocrystal makes the cantilever oscillate above the examined surface with an amplitude of ~2 nm, which exceeds the distance between the probe and the surface. Measuring the amplitude or the shift of resonant frequency in the process of surface scanning allows the microscope to determine the attraction force and construct an image of the surface.

Tapping mode is equivalent to non-contact mode, the only difference being that the cantilever tip slightly touches the specimen surface in the low point of oscillation.

In nanolithography applications, AFM is used in contact mode, and the probe tip moves in accordance with a predefined pattern.

Special cantilevers may be used to examine the electrical and magnetic properties of surfaces.