The analysis of defects by observation of moiré fringes from overlapping crystals—application to zinc sulphide crystals

Abstract

The closure failure b of a Burgers circuit in the distorted lattice is shown to be related to the closure failure αd /2π of the corresponding circuit in moiré fringes by the relation a = 27 2πg . b where g is the index of the plane in the Bragg condition in the faulted crystal and d is the spacing of the moiré fringes. This correspondence is applied to the determination of the fault vectors of stacking faults and partial dislocations in wurtzite zinc sulphide crystals. The stacking faults on (0001) have fault vectors of the type 1/2[2023]. Stacking faults on the prismatic planes {1120} have fault vectors of the type 1/2[1011] or 1/2[1123]. These two fault vectors are indistinguishable by this method. The partial dislocations terminating stacking faults on (0001) are found to have 1/2[0223] as fault vector.