Misfit Accommodation by Screw Dislocations

Abstract

Experiments in which a thin compliant layer, CS, is twist-bonded to a bulk substrate, BS, of the same material showed that heteroepitaxial deposits grown on the compliant layer were of a much higher quality (lower dislocation content) than those grown directly on the substrate. The explanation of this effect is that the compliant substrate, rather than the deposit, elastically deforms to accommodate the misfit and avoids the generation of misfit dislocations in the deposit with their accompanying threading segments. The elastic strain of the compliant substrate is facilitated by the presence of an array of interfacial screw dislocations that lower the energy barrier to sliding in the CS/BS interface. The additional role of the screw dislocations is to reorient their axes in the CS/BS interface to introduce an edge component that accommodates misfit. The geometry and energy of the interfacial dislocations is investigated and the energy changes to accommodate misfit are semi-quantitatively evaluated.