Structural and ferroelectric properties of yttrium substituted bismuth titanium thin films

Yttrium substituted Bi4−xYxTi3O12 (x = 0.00, 0.10, 0.30, 0.50, 0.75, 1.00) polycrystalline thin films were synthesized by metal-organic decomposition method. Ferroelectric measurements revealed that the Bi4Ti3O12 (BTO) films substituted by Y with appropriate ratios could have higher remnant polarization and significantly improved fatigue behavior compared with BTO. The remnant polarization of the Bi3.50Y0.50Ti3O12 capacitor reached 10 μC/cm2 at an applied field about 120 kV/cm with nearly fatigue free property up to 1010 cycles. By using Raman spectra, X-ray diffraction, and scanning electron microscope to analyze the structure and composition of the films, it was found that the Y substitution of Bi at A-site induces changes in film orientation and the lattice distortion that are probably responsible for the improved ferroelectric properties. The microstructure and its relation with the leakage behavior of these thin films were also discussed.