Design and Operation of an Electron Diffraction Camera for the Study of Small Crystalline Regions

The construction and performance of an electron diffraction camera suitable for the examination of crystalline regions of a few hundred Ångstroms extension is described. Goniometric control of the angle of incidence is available under conditions of low contamination. Brief descriptions are given of applications to (a) problems of symmetry including the direct determination of noncentrosymmetric groups, (b) the determination of thickness to an accuracy of one unit cell, (c) the refinement of structure potentials, (d) the measurement of the angular dependence of absorption, (e) the collection of structural data from thin crystals, and (f) the study of imperfect crystals.