Fine Structure of Weak Kinematical Electron Diffraction Beams for a Foil Containing Stacking Fault or Anti‐Phase Boundaries ‐ Two‐Beam Case

A calculation is made of the fine structure of weak kinematic electron diffraction spots arising from small areas containing stacking faults. It is assumed that the illumination conditions are such that there are only two strong beams, i.e. the transmitted beam and a scattered beam. The calculation allows for the fact that the electrons propagating in the weak beam directions originate from these two beams at all depths below the entry surface. The anomalous absorption is considered in the usual phenomenological manner. The analysis leads to four satellites for every weak beam occurring for the two‐beam situation. The intensities of the satellites can, however, vary considerably due to the anomalous absorption. It is then apparent why only a single satellite is usually observed which is in agreement with the simple one‐beam kinematic treatment, which is strictly speaking incorrect. Observations on stainless steel foils are discussed and it is shown that in fact, under good two‐beam situations, there are more complicated satellite configurations as predicted by the refined kinematic treatment.