The influence of elastic anisotropy upon the critical thickness for the plastic relaxation of epitaxial layers was examined with the help of a coupled discrete-continuum simulation. The latter incorporated a rigorous treatment of the boundary conditions and of mismatch stresses, as well as of the elastic properties of a single threading dislocation. Numerical experiments conducted on model Cu/Cu, Cu/Au and Cu/Ni systems, with an (001) interface, showed that (via several distinct effects) elastic anisotropy induced a significant increase in the critical thickness with respect to the predicted values. An isotropic model of a comparison of the anisotropic critical thicknesses for (001) and (111) interfaces showed that Cu-(111) films on Ni substrates were about 50% harder than (001) films.

Dislocations and Elastic Anisotropy in Heteroepitaxial Metallic Thin Films. S.Groh, B.Devincre, L.P.Kubin, A.Roos, F.Feyel, J.L.Chaboche: Philosophical Magazine Letters, 2003, 83[5], 303-13