Cleavage Steps from Screw Dislocations of Inclusion-Growth Spiral Pairs in Stearic Acid Crystal

Abstract
The existence and structure of screw dislocations along the long-chain axis were examined by a careful cleavage technique, in order to characterize the inclusion-growth spiral pairs in stearic acid crystals grown from solution. First, the correspondence between various kinds of dislocation etch pits and the originating centers of cleavage steps on the basal {001} planes was confirmed. Then the cleavage step structures were observed with a reflective Nomarski interference microscope on planes which were created by cutting the crystal between the growth spiral steps and the inclusions. The features of the originating points and the geometrical step structures of the cleavage steps are discussed in relation to the morphological characteristics of the inclusion-growth spiral pairs. As a result, the existence of screw dislocations in the inclusion-growth spiral pairs was clearly confirmed.