backscattered electron

When incident electrons travel a specimen, a part of electrons is reflected (scattered) backward and emitted from the specimen surface. These emitted electrons are called "backscattered electron(s)." The intensity of the backscattered electrons is larger as the atomic number of the constituent atoms in the specimen is larger. The energy of the electrons is close to that of incident electrons, indicating that backscattered electrons possess higher energy than secondary electrons. Thus, the backscattered electrons are emitted from a deep region from the top surface (depth: 100 nm or less) compared to secondary electrons. A backscattered electron image provides the difference of the specimen composition and topographic shape. If the specimen is a crystal, the backscattered electron intensity largely depends on the orientation of the incident electron beam due to electron channeling. Thus, a backscattered electron image obtained from a crystalline specimen shows the difference of the crystal orientation in the specimen.

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