DOMAIN PATTERNS IN EPITAXIAL RHOMBOHEDRAL FERROELECTRIC-FILMS - I - GEOMETRY AND EXPERIMENTS

Possible domain patterns are developed for (001) oriented (pseudocubic indexing) epitaxial rhombohedral perovskite ferroelectric (F-R) films . We assume that the films are grown above their Curie temperature (T- C) in a cubic paraelectric (P-C) state, The rhombohedral distortion co nsists of a ''stretch'' along one of the four [111] crystallographic d irections of the cubic perovskite unit cell. Domain pattern formation is concurrent with the P-C-->F-R transformation on cooling from the gr owth temperature. The domain patterns form to minimize elastic energy in the film, at the energetic expense of both forming domain boundarie s and developing local stresses in the substrate. Eight possible domai ns may form, half of which are related by inversion, thus leading to f our mechanically distinct variants. The possible domain walls are dete rmined by mechanical and charge compatibility and follow closely from the analysis of Fousek and Janovec [J. Appl. Phys. 40, 135 (1969)]. Do main patterns may develop with either {100} or {101} boundaries. In bo th cases, the individual domains in the patterns are energetically deg enerate and thus equal width lamellar patterns are predicted. When pol arization is included in the analysis, the {100} boundary patterns hav e no normal component of the net polarization, whereas the {101} bound ary patterns correspond to the fully poled state. We report on experim ental observation of {100} domain patterns in epitaxial PbZr0.80Ti0.20 O3 and PbZr0.65Ti0.35O3 films. (C) 1998 American Institute of Physics.