Dynamical Theory of the Images of Microtwins as Observed in the Electron Microscope. I. Overlapping Twins

The diffraction contrast at micro‐twins, observed by transmission electron microscopy, is discussed on the basis of the dynamic theory and including anomalous absorption. The diffraction conditions and geometrical properties are analyzed, and their effect on the image deduced. The contrast at overlapping twins is discussed in the case where matrix crystal parts are in reflection position. It is shown that a fringe pattern having similar properties to staking fault patterns may be observed. The analysis does, however, establish criteria which distinguish this image from one due to a stacking fault The properties are illustrated by observations on (101) microtwins in rutile, and analytical conclusions are compared with computed profiles for thick foils and those of intermediate thickness. The conditions existing at twinning dislocations and at the intersection of anti‐phase boundaries with twin boundaries in rutile are discussed.