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Image Formation in the Scanning Electron Microscope

  • D. E. Newbury

Abstract

To understand the process of image formation in the scanning electron microscope, we must examine the component parts of the image formation system: the scanning system, the signal detectors, the amplifiers, and the display. For this discussion, the upper portion of the electron probe forming system, i.e., the electron gun and the upper condenser lenses, is relatively unimportant. Details of these components have been given in the discussion of electron optics in Chapter II. The entire instrument is discussed in detail by Oatley.(1) We shall assume that a focused electron probe of diameter d p is produced by the electron gun and lenses. The components of the image formation system are illustrated in Figure 1, and with this diagram we shall follow the sequence of events in the formation of the image. The electron beam travels down the optical axis of the electron optical column from the gun through the first two condenser lenses with each lens progressively demagnifying the beam. When the beam encounters the first set of scan coils, it is deflected off the optical axis. The second (lower) set of scan coils acts on the deflected beam and produces a second deflection, causing the beam to again cross through the optical axis. The scan coils rest in the bore of the final lens, and during passage
FIGURE 1.

Image formation system in the scanning electron microscope. FA, final aperture; SD, solid state electron detector; ET, Everhart-Thornley electron detector; PM, photomultiplier; S, scintillator; W, ED, wavelength- and/or energy-dispersive x-ray detectors; CRT, cathode ray tube.

of the scan coils, the beam is further demagnified by the action of this lens, which is normally the strongest lens in the microscope.

Keywords

Secondary Electron Backscatter Electron Faraday Cage Contrast Mechanism Picture Element 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Plenum Press, New York 1975

Authors and Affiliations

  • D. E. Newbury
    • 1
  1. 1.National Bureau of StandardsUSA

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