Electron microscopy is an imaging technique that uses an electron beam to probe a material. Since the wavelength of electrons is much smaller than the wavelength of visible light, diffraction effects occur at much smaller physical dimensions. The imaging resolution in electron microscopy is therefore much better than in light microscopy.
The use of electron beams requires that the sample be placed in a vacuum chamber for analysis.
A recent innovation in electron microscopy is the use of several stages of differential pumping between the electron gun and the sample, which is placed in a vacuum of a few torr. This method is called environmental electron microscopy.
TEM images the electrons that pass through a sample. Since electrons interact strongly with matter, electrons are attenuated as they pass through a solid requiring the samples to be prepared in very thin sections.
SEM images the electrons that are reflected from a sample. These images are useful for studying surface morphology or measuring particle sizes.
/chem-ed/imaging/emicrosc.htm, updated 11/3/96
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