AFM: ATOMIC FORCE MICROSCOPE

This is a scanning microscope and it makes a scan of the material surface using a tip of atomic dimensions, placed at the end of a tiny flexible rod. The movements of the rod are induced by forces of inter-atomic interaction at short-range between the tip of the microscope and the atoms of the sample surface; these movements reveal information about the structure of the sample. Basically, the tip of the rod is positioned on a flexible arm, called cantilever, at a distance from the sample surface lower than one nanometer, when the sample is translated along the x-y plane below the tip, repulsion forces or attractive forces are manifested between the sample surface and the tip, with a consequent deflection of the tip in z direction. The morphology of the sample surface is rebuilt by measuring the deflection entity of the tip. In addition, the limitation to analyze only conductive samples doesn't exist with this microscope, in fact a wide variety of samples can be analyzed, for example: plastic, glass and biomolecules.

For example, this spectacular image represents the bottom surface of a plant leaf, observed with an AFM. The openings that are noticed on lower epidermis of the leaf are called stomata; they allow gaseous exchange between the air and the interior of the leaf.

The following figures give the microscope images of the graphite, starting from a vision obtained with an optical microscope (that uses visible light to create a magnified image of an object), up to an image obtained with recent scanning microscopes:

naked-eye view; vision by an optical microscope; vision by a scanning AFM.