  The three scanning electron microscope diffraction based techniques of
electron channelling patterns (ECPs), electron channelling contrast imaging
(ECCI), and electron back scatter diffraction (EBSD) are reviewed. The
dynamical diffraction theory is used to describe the physics of electron
channelling, and hence the contrast observed in ECPs (and EBSD) and ECCI images
of dislocations. Models for calculating channelling contrast are described and
their limitations discussed. The practicalities of the experimental methods,
including detector-specimen configurations, spatial resolution and
sensitivities are given. Examples are given of the use of ECCI for imaging and
characterising lattice defects, both individually and in groups, in
semiconductor heterostructures and fatigued metals. Applications of the EBSD
technique to orientation determination, phase identification and strain
measurement are given and compared with use of ECPs.. It is concluded that
these techniques make the SEM a powerful instrument for characterising the
local crystallography of bulk materials at the mesoscopic scale.
