Elastic interactions of screw dislocations in thin films on substrates

A dislocation image analysis has been developed to study the behavior of dislocations in thin films on substrates. By extending the classical Head solution for one interface between two semi-infinite elastically isotropic media, the image problem for a screw dislocation in a thin film on a substrate has been solved for problems in which additional thin film phases are included, up to the case of four interfaces. The system of an aluminum thin film on an oxidized silicon substrate was used as a model for calculations. The equilibrium position of a single dislocation was determined as a function of stress in the film. Calculations of this kind were also performed for a dislocation dipole in the film. Maximum stresses in the phases immediately adjacent to the thin film were calculated in order to consider when yielding of these phases may occur.