Definition
A scanning electron microscope (SEM) uses an electron beam which scans the object to generate a magnified image of the object from the interactions of the electrons with the object surface.
Structure
The electron beam is generated by an electron source which is usually an electron gun with a heated tungsten filament that thermionically emits the electron beam. To prevent interactions of the electrons with air, the sample is placed in a high vacuum chamber. The images of the sample are shown on a cathode ray tube.
Function
The beam with energy of 0.5–40 keV is focused to a spot of 0.4–5.0 nm in size. It is deflected to scan the specimen in a raster fashion over a rectangular area of the specimen surface. The interaction of the electrons with the surface causes scattering of electrons and emission of electromagnetic radiation. These are detected and amplified and shown on the cathode ray tube where they form a rastered magnified image of the specimen.
The magnification of a...
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References
Versura P, Maltarello MC (1988) The role of scanning electron microscopy in ophthalmic science. Scanning Microsc 2:1695–1723
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Baumeister, M., Kohnen, T. (2016). Scanning Electron Microscopy. In: Schmidt-Erfurth, U., Kohnen, T. (eds) Encyclopedia of Ophthalmology. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-35951-4_420-3
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DOI: https://doi.org/10.1007/978-3-642-35951-4_420-3
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Publisher Name: Springer, Berlin, Heidelberg
Online ISBN: 978-3-642-35951-4
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