Calibration of the Electron Diffraction Camera Constant

1987:91: Millette

Microscope, 35:107-117

Abstract:

The transmission electron microscope (TEM) is used to study the structures of crystals. This is done by examination of the electron diffraction pattern. A factor called the camera constant relates the measurements in a selected area electron diffraction pattern to the structural spacings in a crystal. The camera constant requires calibration and this is usually done with gold or aluminum. The internal-standard technique is a procedure to simultaneously calibrate the camera constant and analyze an unknown by applying a layer of gold on the back side of the TEM grid of the unknown. The camera constant is calibrated and this is used in calculating the d-spacings of an unknown. The d-spacings are compared with known d-spacings (such as the ASTM file) and when a match is found the diffraction pattern can be indexed. Another calibration needed is that of orientation of the image with respect to the diffraction pattern. This calibration is normally done with molybdenum trioxide. This is useful, if the crystal has a “special” habit such as an asbestos fiber, for correlating the diffraction pattern with the image.

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