Scanning Electron Microscopy


The application of electron back scatter diffraction in the scanning electron microscope has been extended to the determination of crystal symmetry elements, point group and space group. The wide angular range of the patterns makes this a relatively simple task compared with equivalent analysis using electron channelling patterns, convergent beam patterns or standard x-ray methods, though the complexity of the analysis does not permit an unthinking approach. To establish the best procedure specimens from the seven crystal systems were investigated and results from the examination of the metal tin (tetragonal), and minerals zircon (ZrSiO4, tetragonal) and calcite (CaCO3 rhombohedral) are presented. The procedure entails determination of the crystal system from detection of rotation axes, determination of point group from the observed combinations of mirror planes and rotation axes, determination of Bravais lattice, and finally, determination of space group from the absences of lines due to screw axes and glide planes. Considerable computational aids were required in the latter stages of analysis and for this a computer program was written to simulate the diffraction patterns from any crystal system and Bravais lattice with line delete procedures to remove lines forbidden because of space group requirements.

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