Preparation and characterization of a- and b-axis-oriented epitaxially grown Bi₄Ti₃O₁₂-based thin films on rutile-type oxides

a- and b-axis-oriented epitaxial Bi₄Ti₃O₁₂ films were prepared on (101)TiO₂ substrates (rutile) at 600°C by metalorganic chemical vapor deposition (MOCVD). Subsequently, the same films were similarly prepared on (101)-oriented conductive materials with the same rutile structure and similar lattice parameters as TiO₂, such as RuO₂ and IrO₂. Their perfect epitaxial growth was confirmed by several X-ray diffraction measurements. RuO₂ and IrO₂ were deposited on not only structurally equivalent (101)RuO₂//(101)TiO₂ and (101)IrO₂//(101)TiO₂ structures, but were also successfully deposited on the corundum (012)Al₂O₃ and (110)Al₂O₃ single crystals by the MOCVD and rf-sputtering method, respectively. A well-saturated P-E hysteresis with a remanent polarization above 20 μmC/cm² was observed for a- and b-axis-oriented Bi₄Ti₃O₁₂-based materials, (Bi_4-xNd_x)(Ti_3-yV_y)O₁₂ (BNTV), that were epitaxially grown on rutile-rutile and rutile-corundum stacking structures. These results should enable broader application of the bismuth layer-structured ferroelectrics.