STRUCTURE AND ENERGY OF 90-DEGREES DOMAIN BOUNDARIES IN BATIO3-TYPE FERROELECTRIC HETEROEPITAXIAL FILMS

90 degrees domain boundaries in PbTiO3/(001)SrTiO3 and PbTiO3/(001)MgO epitaxial films were considered. In contrast to bulk platelike tetrag onal BaTiO3-type crystals, in which the (001) planes of c-domains and the (100) planes of alpha-domains form a nonzero angle (gamma = 3.5 de grees for PbTiO3 crystals), giving rise to surface corrugation, the fi lms, also consisting of 90 degrees domains, have gamma = 0 because the y are rigidly bound to the substrate. A model of a regular dislocation arrangement at the 90 degrees domain boundary was used to calculate t he energy of this domain boundary and the angle gamma as functions of linear dislocation density. At gamma = 0, the energy of the domain bou ndary was found to be substantially higher than at nonzero misorientat ion angles.