STABILITY DIAGRAM FOR ELASTIC DOMAINS IN EPITAXIAL FERROELECTRIC THIN-FILMS

The statics of isolated elastic domains (twins) in epitaxial thin tetr agonal films grown on a cubic substrate is investigated theoretically. Different possible variants of the geometric shape of a domain are st udied: plate, trapezoidal, and triangular. The nonuniform internal str esses, which also exist in polydomain epitaxial systems, are calculate d by the effective-dislocation method. Hence the elastic energies stor ed in heterostructures with different domains are determined. The equi librium width of a domain is calculated by minimizing the total intern al energy of the heterostructure. Next, the stability diagram for isol ated domains in epitaxial films is constructed from energy considerati ons. It is shown that in a large part of this diagram trapezoidal doma ins are energetically more advantageous than plate-shaped domains. The effect of an external electric field on the stability of 90 degrees d omains in epitaxial ferroelectric films is investigated. (C) 1997 Amer ican Institute of Physics.