Scanning electron microscopy

Scanning electron microscopy forms images by rastering a focused electron beam across a specimen and detecting signals emitted from or near its surface.

Secondary electrons: Low-energy electrons emitted from a specimen after excitation by an incoming electron beam. Their surface-sensitive emission provides much of the fine topographic contrast in scanning electron images.
Electron wavelength: The wavelength associated with an electron, which depends on its momentum. Its short value at microscope energies permits imaging beyond visible-light resolution limits.
Energy-dispersive X-ray spectroscopy: An analytical technique that identifies elements by measuring characteristic X-rays emitted from a specimen. Paired with SEM, it maps elemental composition at selected surface locations.
Transmission electron microscopy: An electron-microscopy method that forms images from electrons transmitted through a thin specimen. TEM reveals internal structure through thin samples, unlike SEM's emphasis on surface-emitted signals.
Manfred von Ardenne: A German physicist and engineer who developed early scanning electron microscope designs. His 1930s work established key principles for scanning a focused electron probe.
Backscattered electrons: Incident electrons scattered back out of a specimen, often retaining substantial energy. Their yield varies with atomic number, revealing compositional contrast alongside surface form.
Electron-matter interaction: The scattering, energy loss, and emission processes that occur when electrons enter matter. It determines which signals escape and how deeply they originate in the specimen.
Electron backscatter diffraction: A method that determines crystal orientations from diffraction patterns of backscattered electrons. An SEM can collect these patterns to map grain orientations and crystal phases.
Optical microscopy: Microscopy that uses visible or ultraviolet light and optical lenses to form images. It can image specimens in air and color, but diffraction limits its resolution compared with SEM.
Charles Oatley: A British engineer whose research group developed practical scanning electron microscopes at Cambridge. His group helped turn the early concept into a reliable commercial instrument.

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