Scanning Electron Microscopy and X-Ray Microanalysis by Joseph I. Goldstein download in iPad, ePub, pdf
Magnification is therefore controlled by the current supplied to the x, y scanning coils, or the voltage supplied to the x, y deflector plates, and not by objective lens power. Thus steep surfaces and edges tend to be brighter than flat surfaces, which results in images with a well-defined, three-dimensional appearance. The crystals are captured, stored, and sputter-coated with platinum at cryogenic temperatures for imaging.
Some observations of living insects have been possible however. The improvement arises because secondary electron emission for high-Z materials is enhanced. Nonconductive specimens collect charge when scanned by the electron beam, and especially in secondary electron imaging mode, this causes scanning faults and other image artifacts.
Samples are generally mounted rigidly to a specimen holder or stub using a conductive adhesive. Samples may be sectioned with a microtome if information about the organism's internal ultrastructure is to be exposed for imaging. Ardenne applied the scanning principle not only to achieve magnification but also to purposefully eliminate the chromatic aberration otherwise inherent in the electron microscope. This section does not cite any sources. Due to their low energy, these electrons originate within a few nanometers from the sample surface.
Special high-resolution coating techniques are required for high-magnification imaging of inorganic thin films. The easiest way to get color is to associate to this single number an arbitrary color, using a color look-up table i. Assuming that the display screen has a fixed size, higher magnification results from reducing the size of the raster on the specimen, and vice versa.
Older microscopes captured images on film, but most modern instrument collect digital images. Coating can be difficult to reverse, may conceal small features on the surface of the sample and may reduce the value of the results obtained. The size of the interaction volume depends on the electron's landing energy, the atomic number of the specimen and the specimen's density. This process relies on a raster-scanned primary beam.
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