Once the beam hits the sample, electrons and X-rays are ejected from the sample.ĭetectors collect these X-rays, backscattered electrons, and secondary electrons and convert them into a signal that is sent to a screen similar to a television screen. The beam travels through electromagnetic fields and lenses, which focus the beam down toward the sample. The electron beam follows a vertical path through the microscope, which is held within a vacuum. A beam of electrons is produced at the top of the microscope by an electron gun. The SEM is an instrument that produces a largely magnified image by using electrons instead of light to form an image. How does a SEM work?ĭiagram courtesy of Iowa State University All of these advantages, as well as the actual strikingly clear images, make the scanning electron microscope one of the most useful instruments in research today. Because the SEM uses electromagnets rather than lenses, the researcher has much more control in the degree of magnification. The SEM also has much higher resolution, so closely spaced specimens can be magnified at much higher levels. The SEM has a large depth of field, which allows more of a specimen to be in focus at one time. The scanning electron microscope has many advantages over traditional microscopes. The SEM has allowed researchers to examine a much bigger variety of specimens. Since their development in the early 1950's, scanning electron microscopes have developed new areas of study in the medical and physical science communities. The SEM is a microscope that uses electrons instead of light to form an image. SEM stands for scanning electron microscope.
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