The question of whether the extremely high quality of strained epitaxial films could be retained during subsequent processing, including thermal cycling, was addressed. The present work dealt with the issue of strained film quality degradation via the formation of surface roughness during high-temperature processing; due to the presence of interface misfit dislocations. It was assumed that the layer thickness was initially uniform and that the strain field was uniform. Thus, the chemical potential was constant along the surface. The strain was then partially relieved by the formation of interface misfit dislocations. This resulted in an inhomogeneous strain field along the surface which, in turn, implied the existence of a chemical potential gradient along the surface. A gradient of chemical potential constituted a thermodynamic force, and cause the drift of surface atoms from regions of high potential to regions of low potential. A net change in shape of the surface occurred. It was observed that, for some material systems, the surface shape could take the form of ridges or waves which were correlated with the positions of the underlying misfit dislocations. A numerical method was developed which led to an estimate of the magnitudes and profiles of surface waves under conditions of thermodynamic equilibrium. Beginning from a given initial configuration, the full transient problem was solved numerically in order to describe relaxation to a stable equilibrium shape having a constant chemical potential along the surface.

Computation of Equilibrium Surface Fluctuations in Strained Epitaxial Films due to Interface Misfit Dislocations. F.Jonsdottir: Modelling and Simulation in Materials Science and Engineering, 1995, 3[4], 503-20