DOMAIN CONFIGURATIONS DUE TO MULTIPLE MISFIT RELAXATION MECHANISMS IN EPITAXIAL FERROELECTRIC THIN-FILMS .3. INTERFACIAL DEFECTS AND DOMAIN MISORIENTATIONS

Interfacial defect theory is applied to the epitaxial ferroelectric system consisting of a tetragonal ferroelectric such as BaTiO3 or PbTiO3 grown onto a cubic (001) substrate. The interfacial defects that result from the diffusionless paraelectric to ferroelectric (PE-->FE) phase transition are treated under the constraint that no misfit dislocations are generated during or as a result of the transition. The domain pattern develops to provide strain relief in the film. The interfacial defects for the ...c/a(1)/c/a(1)... domain pattern include coherency edge dislocations and coherency wedge disclinations. Interfacial defects for the ...a(1)/a(2)/a(1)/a(2)... domain pattern include coherency edge and screw dislocations. Far-field strain states for both domain patterns can be predicted from the interfacial defect content. From the twinning geometry, general expressions are derived for the far-field rotations of the crystal axes of individual domains for the ...a(1)/c/a(1)/c... and the ...a(1)/a(2)/a(1)/a(2)... domain pattern. The geometrically predicted rotation angles for ...c/a(1)/c/a(1)... domain pattern are verified by x-ray-diffraction and transmission electron diffraction for epitaxial PbTiO3 films grown on (001) SrTiO3 substrates. (C) 1995 American Institute of Physics.