Atomic-Force Microscopes

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Schematic diagram of AFM [1]

The atomic force microscope (AFM) is a high-resolution type of scanning probe microscopy, with demonstrated resolution of fractions of a nanometer, more than 1000 times better than the optical diffraction limit [1]. The AFM has been used to image the structures on a variety of surfaces. The AFM consists of a cantilever with a sharp tip (probe) at its end that is used to scan the sample surface. The cantilever is typically silicon or silicon nitride with a tip radius of curvature on the order of nanometers. When the tip is brought into proximity of a sample surface, forces between the tip and the sample lead to a deflection of the cantilever according to Hooke's law. Forces that are measured in AFM include mechanical contact force, van der Waals forces, capillary forces, chemical bonding, electrostatic forces, magnetic forces, Casimir forces, solvation forces, etc [1]. The deflection is measured using a laser spot reflected from the top surface of the cantilever into an array of photodiodes.

Reference

[1] http://en.wikipedia.org/wiki/Atomic_force_microscope