Equilibrium structure of epitaxial layers

The equilibrium structure of an epitaxial layer on a flat crystal substrate is considered theoretically. Epitaxial stresses as well as the elastic and free energies of the layer are calculated as function of the substrate crystallographic orientation. It is shown that as the layer thickness increases there is the “phase” transition from the state of the best microscopic fit between the layer and substrate lattices (the microdistortion is absent) to the state of the best macroscopic fit (the elastic energy is a minimum). When the layer thickness increases the epitaxial stress relief due to the formation of elastic domain becomes preferable. In particular cases domains may be twins and the layer is a polysynthetic twin. The formation of the first- and second-order polysynthetic twins is discussed. With the increase in the thickness to some critical value the relaxation by twin domains formation becomes less favourable than by the translation domains formation. The correlation between the translation domains and misfit dislocations is under consideration. [Russian Text Ignored]