Electron microscope

The electron microscope is a microscope that can magnify very small details with high resolving power due to the use of electrons rather than light to scatter off material, magnifying at levels up to 500,000 times.

Types

The Transmission electron microscope (TEM) produces images by detecting electrons that are transmitted through the sample, while the Scanning electron microscope (SEM) produces images by detecting secondary electrons which are emitted from the surface due to excitation by the primary electron beam.

Related Topics:
Transmission electron microscope - Scanning electron microscope

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Generally, the TEM resolution is about an order of magnitude better than the SEM resolution, however, because the SEM image relies on surface processes rather than transmission it is able to image bulk samples and has a much greater depth of view, and so can produce images that are a good representation of the 3D structure of the sample.

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In both types of microscope, high voltage electron beams from a cathode are focused by magnetic lenses on to the specimen. In the TEM, the transmitted beam is magnified by a series of magnetic lenses until they hit a flourescent screen, photographic plate, or light sensitive sensor to produce an image on a monitor or computer. In the SEM, the electron beam is rastered across the sample, with detectors building up an image by mapping the detected signals with beam position.

Related Topics:
Voltage - Cathode - Magnet

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A Scanning Transmission Electron Microscope (STEM) is a specific sort of TEM, where the electrons still pass through the specimen, but, as in SEM, the sample is scanned in a raster fashion.

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