Investigation of crystal surface structure by reflection electron diffraction

A program of experimental observations of the angular dependence of the secondary electron image contrast and reflection electron diffraction (RED) patterns was carried out utilizing an instrumental system which combines scanning electron microscopy (SEM) and RED in an ultra high vacuum environment. The experimental results for pyrolytic graphite specimens were interpreted with the help of computed RED intensities and Bloch wave extinction depths. These were obtained from a program based on an n-beam dynamical electron diffraction formulation. The results of this comparison showed that the enhanced crystallographic contrast originated from variations in the penetration depth of the incident electron beam caused by different azimuthal incidence angles with respect to the crystal lattice. A series of instrumental improvements which were designed to remove deficiencies found during the experimental work are described