Epitaxial BaTiO3 thin films grown on MgO-buffered R-plane-cut Al2O3 substrates showed a non-uniform distribution of planar defects. Transmission electron microscopy allows the determination of the distributions of planar defects with respect to the Al2O3 substrate. The BaTiO3 film, the MgO buffer and Al2O3 substrate orientations exhibited the relationships: [100]BaTiO3||[100]MgO||[11•0]Al2O3, (010)BaTiO3||(010)MgO||(11•4)Al2O3 and (001)BaTiO3||(001)MgO||≈(1102)Al2O3 (about 5° deviation). Under the above relationship, most of the {111} stacking faults occur on (111) and (111) planes, that was two of four sets of {111}BaTiO3, whereas cracks in the BaTiO3 film (and MgO buffer) were situated on the (100) planes. The anisotropic distribution of planar defects was regarded as a consequence of an anisotropic stress in the films generated during their fabrication.

Anisotropic BaTiO3 Thin Films Grown on MgO-Buffered R-Plane Sapphire. C.H.Lei, G.Van Tendeloo: Philosophical Magazine Letters, 2002, 82[8], 433-42