Secondary electron
= Secondary electron
A <secondary electron> is emitted from a material after excitation by incident radiation or particles, rather than simply being a high-energy primary <electron> redirected back out. Many detected secondaries have low enough <kinetic energy> that escape strongly favors regions near a surface.
This makes secondary-electron collection useful for <secondary-electron topographic contrast> in a <scanning electron microscope>. Surface angle, local <electric fields> and collector bias affect the signal as well as emission itself. Backscattered primaries can also excite secondary <electrons> away from the probe's immediate landing position, so every detected secondary need not originate directly beneath the nominal probe.<Secondary electron by JEOL Ltd.>[Surface-related emission and distinction between secondary-electron generation paths]{ref}