Measurement of the lattice displacement across {100} platelets in diamond by large-angle convergent-beam electron diffraction

Large-angle convergent-beam electron diffraction is used to measure the displacement across {100} (R00) platelets in an Argyle brown diamond. By examining the intersection of a series of two-beam diffraction contours g with an inclined platelet, it is shown that integral and fractional components of g.R can be separately determined. The integral part of g.R is determined by applying standard Cherns-Preston rules to the image of the bounding partial dislocation. The fractional part / of g.R is determined by comparing the rocking curve in the faulted region with two-beam dynamical simulations. It is shown that the rocking-curve asymmetry at small deviation parameters provides a simple measurement of f which is relatively unaffected by background inelastic scattering and a finite probe size. Higher-order reflections are used to improve sensitivity, giving R = 0.40±0.01. This result is compared with measurements obtained by other techniques and its significance for understanding the structure of diamond platelets is discussed.