Electron Detectors and Spectrometers

The most effective detection systems for secondary electrons (SE), which has a low noise level and a large bandwidth, is the Everhart-Thornley detector. Electrons are collected by a positively biased grid in front of a scintillator biased at +10 kV. The light emission is recorded by a photomultiplier tube. Scintillation detectors can also be used for backscattered electrons (BSE) when the solid angle of collection is increased. Other alternatives for BSE are semiconductor detectors, microchannel plates, or the conversion of BSE to SE. The recording of SE in the in-lens mode or in LVSEM needs special detector designs for rotationally symmetric collection fields. For the separation of different types of contrast and for more quantitative signals, improvements can be obtained by employing multiple detector systems.