Scanning Electron Microscopy

An electron microscope called a scanning electron microscope SEM scans a sample's surface with a concentrated stream of electrons to create pictures of the material. As the electrons contact with the sample's atoms, different signals emerge that provide details about the sample's surface topography and composition. A raster scan pattern is used to scan the electron beam, and a picture is created by combining the detected signal's strength with the beam's position. Using a secondary electron detector, the most popular SEM mode detects secondary electrons released by atoms stimulated by the electron beam Everhart–Thornley detector. The specimen topography affects, among other things, the quantity of secondary electrons that may be detected and, consequently, the signal intensity. Some SEMs can provide resolutions that are superior to 1 nm. Specimens are examined at a variety of cryogenic or high temperatures using specialist equipment, as well as in high vacuum in a normal SEM, low vacuum or wet circumstances in a variable pressure or environmental SEM, and both dry and wet conditions in a typical SEM.