Effect of Bi3.25La0.75Ti3O12 Seeding Layer on Ca0.4Sr0.6Bi4Ti4O15 Thin Film

Bilayered ferroelectric thin films, Ca0.4Sr0.6Bi4Ti4O15 grown on Bi3.25La0.75Ti3O12, were prepared on (100) Si substrate by a sol-gel method. The thin films were annealed at 700 degrees C under air atmosphere. Phase structure, orientation and morphology of the bilayered ferroelectric thin films were characterized by X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) respectively. At the same time, the P-E hysteresis loops of both films were measured. Compared with pure Ca0.4Sr0.6Bi4Ti4O15 thin film, Ca0.4Sr0.6Bi4Ti4O15 thin film grown on Bi3.25La0.75Ti3O12 seeding layer has larger a-axis orientation degree and larger grain size of about 80 nm. And there are less voids in bilayered ferroelectric thin films exhibiting a uniform and dense surface. Meanwhile, the bilayered ferroelectric thin film shows higher P-r=13.34 mu C/cm(2), and the corresponding coercive field is 68.32 kV/cm. The results suggest that Bi3.25La0.75Ti3O12 film layer plays an important role on nucleation and crystallographic orientation of Ca0.4Sr0.6Bi4Ti4O15 thin film, and it is vital to the improvement of remanent polarization.