The variants, domains and defects in the CoSi//Si(111) epitaxial system

Abstract

This paper presents a study of defects in the CoSi//Si(111) epitaxial system which arise due to the difference in symmetry between the epilayer and the substrate. Using simple group theory, two energetically degenerate orientational variants are predicted and they are identified using transmission electron diffraction. Both orientational variants are predicted to contain a maximum of four domains, each with a different interfacial structure. Using dark-field imaging, at least two of the four domains are identified, and a difference in their relative proportions confirms the non-degeneracy. Finally, a topological theory of interfacial defects is used to show that dislocations with 1/3 <110> _CoSi Burgers vectors are likely to relieve the misfit strain in the epilayer. These are then identified in the bicrystal using a combination of weak-beam imaging and a direct measurement of the moiré fringe spacings.