Some Aspects of Coherent Epitaxial Deposits
Résumé
energy (surface tension, interface tension, angle of contact, etc.) PACS.68.10.Gw-Interface activity, spreading PACS.68.55.-a-Thin film structure and morphology Abstract. 2014 When wetting is complete, coherent epitaxies on a thick planar substrate B build up z continuous pseudomorphous layers A which are fully strained according to their natural misfit m. The so-accumulated strain energy density is responsible for some remarkable facts: 1) Each layer is formed at precise undersaturation. At saturation there is a specific number of wetting layers z0. 2) Such layers accumulate strain energy and then may relax plastically by interfacial dislocations at a critical thickness zd1. 3) At some other critical thickness zSK, (z0 zSK zd1), the monolayer growth becomes less stable than layer thickening, what leads to three-dimensional (3D) islanding on the zsk wetting layers, called Stranski-Krastanov (SK) growth. Such islands laterally relax and, since coherent with their substrate, drag the substrate which relaxes too. 4) If the equilibrium shape ratio r of non misfitted 3D deposit (m = 0) depends on the wetting, for a misfitted (m ~ 0) and relaxed crystal, the strain opposes to wetting, so that the higher the elastic energy, the greater the shape ratio rm. 5) Since the equilibrium shape of a 3D crystal depends upon strain, at each dislocation entrance the shape ratio of the crystal varies in a sudden way.