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Scanning Electron Microscope
A JEOL JSM 5400. Allows users to perform conventional secondary electron imaging, backscatter electron imaging, X-ray micronanalysis and cryo-SEM.
Details
The scanning electron microscope is an instrument which uses a lens system to focus electrons generated from an electron gun to a fine point at the surface of a conductive sample.
The focused beam interacts with the specimen reflecting electrons which may be absorbed by the sample and subsequently give rise to light (cathode luminescence), electric current, low energy secondary electrons, backscatter electrons, and x-rays.
The most useful for imaging include the secondary electrons which are generated at the points where the beam interacts with the sample and subsequently attracted to a detector composed of grid held at a low 50eV positive potential, a scintillator and photomultiplier tube. The number of secondary electrons are dependent upon atomic identity, topography and sample orientation at the point of impact.
The electron beam is deflected along a straight line on the sample and terminated at the end of the area set by the magnification selected. It is then returned to the starting point, moved down a short distance and repeated along a line parallel to the first until and area rectangular in shape is scanned. The series of lines constituting the scanned area is referred to a raster. Deflector coils on the CRT are in synchronization with the scanning coils affecting the SEM beam but the raster on the CRT is kept constant while area scanned on the sample can be changed. The ratio if the linear size of the two rasters is the magnification.
Images generated on the JSM 5400 in the EMF can be recorded on Polaroid film, a Sony video printer or archived on the Princeton Gamma Tech Image Analysis system.