Line tension of extended double kinks in thin films

Abstract

We derive an expression for the dislocation line tension in thin-film structures for double-kink (dislocation dipole) extension of a threading dislocation. From these calculations, we conclude, that for a double kink that is a distance of more than three times the vertical dipole separation from the free surface, the effect of the free surface on the double-kink line tension is insignificant. We consider the specific case of a double-kink bounding a 60-nm-thick Si0.7Ge0.3 strained layer grown on a silicon substrate and buried under a silicon cap. For this specific configuration, line tension is seen to increase with cap thickness (which is equivalent to distance of the double kink from the surface) only up to a cap thickness of 100 nm.