Observation of the elastic field related to a structural domain boundary along a {111}NiSi 2//{115}Si heterotwin interface

A (111)NiSi ₂//(115)Si heterotwin interface has been observed by high resolution electron microscopy (HREM) along the common direction [110]NiSi ₂//[110]Si to identify the long period atomic structural units (ASU's). Coexistence of two different structural domains has been found with ASU's corresponding to two different cycles of five-, six-, and seven-atom rings. A dislocation/ledge (DL) has been particularly studied because its separates these two unusual cycles of ASU's. The elastic displacement field u of the atom columns around the DL has been calculated using both crystallographic and anisotropic elasticity properties of the crystals, assuming a two-dimensional u field. From a comparison between the positions of the atom columns as derived from elasticity calculations and as deduced from the HREM image, it is concluded that the DL is a mixed dislocation with the Burgers vector (-1/4)[111]NiSi ₂ + (1/2)[110]Si = (1/12)[515]Si, a result also in agreement with the imperceptible ledge height associated with the DL core. Such a Burgers vector underlines the role of the Si matrix dislocations for producing such structural domains.