Overview of Atomic Force Microscopy

Atomic force microscopy or AFM is a method to see a surface in its full, three-dimensional glory, down to the nanometer scale. The method applies to hard and soft synthetic materials as well as biological structures (tissues, cells, biomolecules), irrespective of opaqueness or conductivity. The 3D object is not perceived in the usual way, that is, by line-of-sight, reflections or shadows. (Or, as with scanning electron microscopy, by secondary electron emission enhanced or suppressed to give the perception of reflections and shadows.) Rather, at each point or pixel in the image a measurement of surface height is made (with caveats). Typically one chooses to display these heights as colors, usually some variant of dark-is-low, bright-is-high, with a gradient of color (say redorange-yellow) or grayscale in between. Thus a multicolor image of surface topography typically is obtained, for viewing purposes.