Atomic Force Microscope: Working principle (Atomic Level Forces)

Lennard -Jones Potential: interaction b/w two atoms when spaced by ~nm

Atomic Force: gradient of potential

Figure 19.03: Variations of force with probe distance from sample [2].

Figure 19.03 shows the variation of forces with the probe distance from the sample surface. As the probe distance is very close the samples surface, the probe is in hard contact with the surface (called as repulsive regime). On moving the probe away from the surface, the probe is pulled towards the surface in certain range, called as an attractive regime. Moving the probe far away from the surface would result in no deflection due to no interactive force between the probe and sample surface.

Ref.[2]. Ref.: G.A. Tsongas et al, J. Phys. B (ATOM. MOLEC. PHYS.) SER. 2 (1969) 437.