Everhart-Thornley detector

Figure 4.3 Signal collection by the Everhart-Thornley detector. B, backscattered electron trajectory SE, secondary electron trajectory F, Faraday cage S, scintillator LG, light guide PM, photomultiplier tube. (Reproduced with kind permission of Springer Science and Business Media from J.I. Goldstein et al, Scanning Electron Microscopy and X-ray Microanalysis, 2nd ed., Plenum Press, New York. 1992 Springer Science.)...

Shadow contrast. This is the shadowing of the SE signal due to holes or protrusions. The amovmt of shadowing depends on the presence of electrostatic and magnetic extraction fields on the surface. Shadowing is less for detection through the lens as compared with that of the standard Everhart-Thornley detector. 

Transducers. Secondary electrons are most often detected by a scintillator-photomultiplier system, called the Everhart-Thornley detector and illustrated in Figure 21-22. The secondary electrons strike a scintillator that then emits liaht. The emitted radiation is carried... 

Both secondary and backscattered electrons may be detected with an ESEM. The Everhart-Thornley detector shown in Figure 21-22 cannot be used because the high bias voltage of the scintillator would cause electrical breakdown at high pressures. Instead, gas-phase secondary electron detectors, which make use of cascade amplification, are employed. These not only enhance the secondary electron signal but also produce positK e ions, which are attracted to the insulated specimen surface and suppress charging artifacts. Earge-area scintillation detectors can be used to detect back-scattered electrons as with conventional SEM systems. 

SEs and BSEs are typically detected by an Everhart-Thornley (ET) scintillator-photomultiplier secondary electron detector. The SEM image is shaped on a cathode ray tube screen, whose electron beam is scanned synchronously with the high-energy electron beam, so that an image of the surface of the specimen is formed [52], The quality of this SEM image is directly related to the intensity of the secondary and/or BSE emission detected at each x- and y-point throughout the scanning of the electron beam across the surface of the material [8],... 

SEs have energies less than about 20eV, while BSEs have energies ranging up to that of the incident electrons. Due to the wide energy difference between the SEs and BSEs (usually several thousand eV), it is possible to easily separate the two signals. A typical Everhart/Thornley SE detector (3) is shown in Fig. 2. This consists of a mesh, to which a positive potential of a few hundred volts is... 

Everhart-Thornley secondary electron detector, 612 Exchange, chemical in NMR, 519. 

The detector in the SEM that is normally used for imaging is the Everhart-Thornley scintillator/photomultiplier (E-T detector). This is a low-noise, high-speed and efficient detector that detects a small fraction of the... 

FIGURE 4 The Everhart-Thornley secondary electron detector. 

SE Detector Everhart-Thornley Gaseous secondary electron detector... 

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