SE1

Secondary electron(s) which are excited directly by the incident electrons (primary electrons along the incident electron path. SE1 possesses the information on the shape and constituent materials of a specimen near the incident electrons. SE1 is used to form a secondary electron image. The energy of a secondary electron is a few 10 eV at maximum.
The primary electrons repeat inelastic scattering and diffuse into the deep region of the specimen. The secondary electrons excited in the deep region do not reach the specimen surface because they have small energies and are scattered in the specimen. The escape depth, the maximum depth, from which a secondary electron can escape beyond the specimen surface, is 5 to 10 nm for most metals. Only the secondary electrons (SE1s) generated within this depth contribute to form the secondary electron image.
The schematic of the S1 generation process is illustrated below.

Fig. Generation process of SE1

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