The AFM consists of a cantilever with a sharp tip at its end. Multiple white LEDs illuminate the sample for proper positioning and setup. The tip is brought into close proximity of a sample surface. The force between the tip and the sample leads to a deflection of the cantilever according to Hooke's law. Typically, the deflection is measured using a laser spot reflected from the top of the cantilever. The tip is then scanned across the sample surface and the vertical displacement s necessary to maintain a constant force on the tip is recorded. The resulting map of s(x,y) represents the topography of the sample. There are two modes of operation- contact mode and dynamic mode. In the contact mode operation, the force between the tip and the surface is kept constant during scanning by maintaining a constant deflection. In the dynamic mode, the cantilever is externally oscillated close to its resonance frequency. The oscillation gets modified by the tip-sample interaction forces; these changes in oscillation with respect to the external reference oscillation provide information about the sample's characteristics. The dynamic mode generates lower lateral forces on the sample and is widely used to image biological samples. AFM can work perfectly well in an ambient or even liquid environment.
Atomic force microscope system(Easyscan 2 STM version 1.5)