The inability of optical microscopes to image sizes smaller than the wavelength of visible light resulted in the invention of nanoscopes in the last decades. AFM is at the top of the list due to its low price and multi-applications.

The basic principle of AFM A spring micron-sized cantilever has a conical tip at its free end. The conical tip with a very sharp end, usually less than 10 nanometres, scans the sample surface from a very close nanometric distance.
As the tip moves over the surface, the Van Der Waals forces between atoms on the sharp end of the tip and atoms on the sample’s surface vary, resulting in vertical displacements of the cantilever.
Vertical movements of the cantilever are sensed by an optical method. The reflected laser beam from the cantilever backside hits a quadruple photodiode. The output signals of the photodiodes are related to the vertical movements of the cantilever, which in turn represents the sample’s surface topography.
Nowadays, AFM is the main tool in Nano research works. Apart from 3-dimensional nanoimaging, AM can determine various properties of the sample on a nanoscale; AM could also perform nano-manipulations and nanolithography.