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Atomic Force Microscope (AFM)

An Atomic Force Microscope (AFM) consists of a Si or Si3N4 microscale cantilever

that has a very sharp tip (usually 5-15nm radius). The tip is brought to very close proximity to the sample surface and scanned laterally across the surface. Forces (such as mechanical contact, Van der Waals, capillary, chemical bonding, electrostatic, magnetic, etc.) between the tip and the atoms on the sample surface lead to vertical deflections of the cantilever according to Hooke’s Law. By monitoring the deflection using a laser spot reflected from the top of the cantilever onto a position sensitive photodetector array, one can construct a 3-dimensional topographic map of the sample surface. Typical image lateral resolution is in the order of the tip radius, although atomic resolution can be achieved in non-contact mode, as well. The vertical resolution can be in the order of angstroms. AFM is applicable to both electrically conductive and insulating samples and requires very little sample preparation procedures.