The theory of interfacial defects was applied to an epitaxial ferroelectric system which consisted of a tetragonal ferroelectric material that had been grown onto an (001) cubic substrate. The interfacial defects that resulted from the diffusionless, paraelectric to ferroelectric, phase transition were treated within the constraint that no misfit dislocations were generated during, or as a result of, the transition. The domain pattern developed so as to produce strain relief in the film. The interfacial defects for the ...c/a1/c/a1... domain pattern included coherency edge dislocations and coherency wedge disclinations. The interfacial defects for the ...a1/a2/a1/a2... domain pattern included coherency edge and screw dislocations. Far-field strain states for both domain patterns could be predicted on the basis of the interfacial defect content. From the twinning geometry, general expressions were derived for the far-field rotations of the crystal axes of individual domains for the ...c/a1/c/a1... and ...a1/a2/a1/a2... patterns. The geometrically predicted rotation angles for the ...c/a1/c/a1.. domain pattern were verified by applying X-ray diffraction and transmission electron diffraction techniques to epitaxial PbTiO3 films on (001) SrTiO3 substrates.

J.S.Speck, A.C.Daykin, A.Seifert, A.E.Romanov, W.Pompe: Journal of Applied Physics, 1995, 78[3], 1696-706