by Noriyuki Inoue, SEM Applications Scientist, JEOL USA
Scanning electron microscopy (SEM) is an imaging technique that produces images of a sample by scanning the surface with a focused beam of electrons. SEM differs from optical microscopy, as it uses electrons instead of light to “see” into materials. When comparing SEM to optical microscopy, optical microscopy is limited by the wavelength of light, which is physically set in a defined range. SEM has the advantage of breaking this limit and allows for resolution that can reach the sub-nanometer level.
SEM has a large depth of field and higher magnifications than traditional optical microscopy. This, combined with its ability to conduct chemical analyses using spectroscopic methods, makes it a very powerful research tool. SEMs provide a high degree of analytical capability and reveal surface details at nanoscale resolution. A single image from SEM can often be enough to achieve critical objectives i.e., visualizing microstructures. There are many types of SEMs, ranging from the more common type, which use a tungsten filament as an electron source, to the more specialized type which, with a field emission (FE) electron gun mounted, attains higher resolution and magnification.
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