Atomic force microscopy (AFM)

Atomic force microscopy (AFM) was introduced in 1986 by G. Binnig, C.F. Quate and C. Gerber. Gerber [1] as an application of the scanning tunneling microscope (STM) concept. to study the surfaces of insulating materials on an atomic scale. By combining the principles of the scanning tunnelling microscope and the profilometric stylus, the authors demonstrated the possibility of imaging, in open air, the surface of conductive or non-conductive samples, with a lateral resolution of 30 Å and a vertical resolution of less than 1 Å. Since then, the technique has been adapted to a variety of environments, including vacuum, liquids, low temperatures and magnetic fields, as well as for applications in chemistry and biology.

AFM is based on the measurement of forces between a thin stylus and the surface under study. The force transducer is a leaf spring (stylet) embedded at one end and fitted with a tip at the other, also known as a "cantilever". Interacting forces modify the static or oscillating deflection or torsion of the stylus. In today's force microscopes, cantilever deformations are most often measured by deflecting a light beam ("laser diode") reflected by the tip of the stylet, a method proposed as early as 1988 by G. Meyer and N. Amer [2] .

The development of this local probe method has been rapid, both in university laboratories and in industry. Control tasks on production lines are routinely carried out using this relatively simple-to-use device. Most users are looking to obtain characteristic surface shapes or sizes; by scanning the sample under the "cantilever", the desired AFM image is obtained. However, it soon became apparent that the same instrument could also be used to provide original "nanometer physics" situations.

In the first part, the instrumentation is described and the various operating modes (contact, resonant, tapping, friction, etc.) are presented in general terms. Emphasizing the instrument's potential, the fundamentals of the main methods used are explained, without being exhaustive. In the second part, physical applications in various fields are presented.