Generation of grown-in dislocations at NiCu misfit boundaries during three-dimensional nucleation and growth

Abstract

The origin of a high density of grown-in dislocations in electrolytic nickel films grown epitaxially on bulk single-crystal Cu{001} and their relationship to misfit dislocations were investigated using transmission electron microscopy. Consistent with previous observations, two types of misfit dislocation were found to be present at the NiCu interface; the first type had the mixed Burgers vector of 1 2 〈011〉 inclined at 45° to the interface and it probably originated from the deposit top surface and slipped into the interface. The second type, being most effective in accomodating an interfacial lattice misfit (about 2.5%), had the Burgers vector of 1 2 〈110〉 which is parallel to the interface. Weak-beam imaging revealed that these two types of dislocation were segmented, actually forming a half-loop, suggesting that they must have been generated locally during three-dimensional nucleation and growth stages. Furthermore, these half-loop segments are replicated into the deposit side approximately perpendicular to the interface and eventually become a part of grown-in dislocations. The second type, the origin of which was not well understood previously, is shown to be generated during coalescence of three-dimensional epitaxial islands. The segmentation of misfit dislocations is found to be responsible for the production of the high density of grown-in dislocations observed in epitaxially grown nickel deposits on copper.