Anisotropic BaTiO_3 thin films grown on MgO-buffered R-plane sapphire

摘要

Epitaxial BaTiO_3 thin films grown on MgO-buffered R-plane-cut Al_2O_3 substrates show a non-uniform distribution of planar defects. Transmission electron microscopy allows the determination of the distributions of planar defects with respect to the Al_2O_3 substrate. The BaTiO_3 film, the MgO buffer and the Al_2O_3 substrate have an orientation relationship of [100]_(BaTiO_3)//[100]_(MgO)//[1(1-bar)20]_(Al_2O_3), (010)_(BaTiO_3)//(010)_(MgO)//(1104)_(Al_2O_3) and (001)_(BaTiO_3)//(001)_(MgO)//250L?1(1-bar)02_(Al_2O_3) (about 5 ° deviation). Under the above relationship, most of the {111} stacking faults occur on (111) and ((1-bar)11) planes, that is two of four sets of {111}_(BaTiO_3), whereas cracks in the BaTiO_3 film (and MgO buffer) are situated on the (100) planes. The anisotropic distribution of planar defects regarded as a consequence of an anisotropic stress in the films generated during their fabrication.