Misfit dislocations in screw orientation

Abstract

If the coherency strain induced in an epitaxial crystal is a shear without dilatation it can be accommodated by a network of screw dislocations. If the crystal is rotated away from epitaxy about the normal to the interface plane, the misfit dislocations retain their screw orientation and the energy of the interface decreases. This decrease persists until the misalignment (in radians) becomes equal to half the shear strain needed to accommodate all the misfit. Thereafter, misalignment is accompanied by an increase in interfacial energy. Dilatation of the crystal rotates the screw dislocations into mixed orientation.