It was pointed out that, although the density of misfit dislocations which threaded a growing hetero-epitaxial thin film could be considerably reduced by using a compliant substrate, the physical mechanism was not clearly understood. Most theoretical models supposed that the growing film could relax in an elastic manner by slipping on this type of substrate. However, this idea required the supposition of macroscopic slip displacements. Such displacements were disregarded in the usual theories, and were not reported to occur in practice. This very dubious free-slipping hypothesis was used to establish a force balance (strain partitioning) between the growing film and the template layer below it. This then led to an enhanced critical thickness for the onset of slip of misfit dislocations. More realistic mechanisms were considered here, including early plastic relaxation at a low film thickness; where the multiplicative interaction of dislocations hardly ever occurred.

Principles of Strain Relaxation in Heteroepitaxial Films Growing on Compliant Substrates. G.Kästner, U.Gösele: Journal of Applied Physics, 2000, 88[7], 4048-55