EQUILIBRIUM MICROSTRUCTURE OF EPITAXIAL THIN-FILMS

A theoretical study is presented of he equilibrium domain microstructu re expected for a thin film grown epitaxially onto single-crystal subs trate as a function of temperature, film thickness, and lattice misfit for the case when the film can undergo a structural phase transition. The theory treats the epitaxial interface at the level of the Frenkel -Kontorova model and takes into account domain-wall energies and bulk- elasticity effects in both the film and the substrate. Existing predic tions for this problem by Roitburd are reproduced when the epitaxial i nterface is commensurate. Results are obtained for the general case wh en the interface is incommensurate. The corresponding domain structure generically involves multiple phases.