DOMAIN CONFIGURATIONS DUE TO MULTIPLE MISFIT RELAXATION MECHANISMS INEPITAXIAL FERROELECTRIC THIN-FILMS .3. INTERFACIAL DEFECTS AND DOMAINMISORIENTATIONS

Interfacial defect theory is applied to the epitaxial ferroelectric sy stem consisting of a tetragonal ferroelectric such as BaTiO3 or PbTiO3 grown onto a cubic (001) substrate. The interfacial defects that resu lt from the diffusionless paraelectric to ferroelectric (PE-->FE) phas e transition are treated under the constraint that no misfit dislocati ons 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 defec ts 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 p atterns 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 geomet rically predicted rotation angles for ...c/a(1)/c/a(1)... domain patte rn are verified by x-ray-diffraction and transmission electron diffrac tion for epitaxial PbTiO3 films grown on (001) SrTiO3 substrates. (C) 1995 American Institute of Physics.