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SEM

SEM: Scanning electron microscopy/microscope
Definition:A microscopy technique in which a focused electron beam is scanned over a small area of a sample and the resulting signal (e.g. intensity of secondary electrons) is used to plot a magnified image of the scanned area.
Explanation:In a SEM, a finely focused and highly accelerated electron beam is scanned across regular grid points over the surface of a sample. The interaction of the primary beam electrons with the surface of the material leads to the formation of a number of different signals which can be collected by different detectors. This signal is then used to modulate the intensity of a magnified image of the scan grid that is displayed on a monitor. The smaller is the scan grid on the sample, the larger is the magnification. Also, the smaller is the beam diameter, and the smaller is the physical interaction volume between beam and sample, the better is the resolution of the microscope. Samples for an SEM usually need to be conductive, vacuum resistant and charge resistant.

A number of signals that give different information on the sample can be selected. Some of them are compiled in the following table:
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Diagram:

SFB-Link:SEM is a very powerful and comprehensive way to characterize many aspects of solid samples, including chemistry, crystallography and morphology.
References:Goldstein J, Newbury DE, Joy DC, Lyman CE, Echlin P, Lifshin E, Sawyer L, Michael JR. Scanning Electron Microscopy and X-ray Microanalysis, 3rd ed. New York: Springer; 2007