The effect of a difference in the elastic constants of an epilayer and its substrate, upon the critical thickness of an epilayer, was investigated in terms of isotropic elasticity. The results indicated that the self-energy of a mismatch dislocation was controlled by the soft phase between the epilayer and the substrate, while the interaction energy depended only upon the elastic constants of the thin film. It was easier for a dislocation to form if the substrate was softer than the film, and the critical thickness was therefore smaller. On the other hand, a soft epilayer could be very thick without containing any mismatch dislocation.

Effect of Elastic Constants on the Critical Thickness of an Epilayer. T.Zhang: Physica Status Solidi A, 1995, 152[2], 415-29