Stress relaxation and critical layer thickness of high temperature superconductor thin films, heterostructures and superlattices

The heteroepitaxial growth of high temperature superconductor thin films on single crystal substrates produces strained heterostructures when the mismatch is small and the thickness of the epilayer is not large. Although a large number of studies have been carried out in the case of semiconductor epitaxy, only a few papers report models or experimental results dealing with the relaxation of the elastic strain in cuprate heterostructures. The authors apply here the calculations performed for semiconductor epitaxial layers and pseudomorphic superlattices to estimate the critical layer thickness of cuprate thin films, heterostructures and superlattices. The result of these calculations is discussed with respect to the previously reported data and also to the results in the case of YBaCuO heterostructures. 50 refs., 8 figs., 1 tab