Atomic Force Microscope

The Atomic Force Microscope (AFM) is a very high-resolution type of scanning probe microscopy. The precursor to the AFM, the scanning tunneling microscope, was developed by Gerd Binnig and Heinrich Rohrer in 1981, a development that earned them the Nobel Prize for Physics in 1986. Binnig, Quate and Gerber invented the first AFM in 1986. The AFM is one of the foremost tools for imaging, measuring and manipulating matter in the field of nano-technology. The primary modes of operation are contact (static) mode and non-contact (dynamic) mode. In the contact mode operation, the static tip deflection is used as a feedback signal. The low stiffness cantilevers are used to boost the deflection signal. However, close to the surface of the sample, attractive forces can be quite strong, causing the tip to 'snap-in' to the surface.

Thus static mode AFM is almost always done in contact where the overall force is repulsive. In contact mode, the force between the tip and the surface is kept constant during scanning by maintaining a constant deflection. In the non-contact mode, the cantilever is externally oscillated at or close to its fundamental resonance frequency or a harmonic. The oscillation amplitude, phase and resonance frequency are modified by tip-sample interaction forces; these changes in oscillation with respect to the external reference oscillation provide information about the sample's characteristics. Stiff cantilevers provide stability very close to the surface and, as a result, this technique was the first AFM technique to provide true atomic resolution in ultra-high vacuum conditions.


SPA-400 (SII Nano-Technology Inc. )