Compliant effect in twist-bonded systems

Abstract

We describe how a buried twist-bonded interface closely set below the substrate surface alters the plastic relaxation in heteroepitaxy. For this, first—considering from an atomistic point of view, two twist-bonded semi-infinite substrates—we calculate and compare the elastic energy for several twist angles. We find that for ‘low twist angles’ (up to around 20°), the twist-bonded interface can be reconstructed without involving any dangling bonds, but for large twist angles, the twist-bonded interface becomes more unstable and involves some dangling bonds. Furthermore, for ‘low twist angles’, the strain field induced by such a twisted interface does not extend on more than several atomic layers. Second—considering a mesa made from a thin twist-bonded layer and a thick 4% compressive strained overlayer—we study the motion of edge dislocations while entering from the edge and moving towards the centre of the sample. The energy barrier at edges contravenes the introduction of a rectilinear edge dislocation at the mesa bottom interface. As far as misfit edge dislocations are concerned, it is easier to introduce it at the heterojunction between the compressive strained overlayer and the thin twist-bonded layer than at the mesa bottom twisted interface. Finally, we define a kinked edge dislocation which is able both to relax more energy than the rectilinear one and to weaken the energy barrier at the edges of a mesa, so that compliancy may become possible.