Characterization of ferroelectric Bi3.25La0.75Ti3O12 thin films prepared by metal organic decomposition method

Ferroelectric Bi3.25La0.75Ti3O12 (BLT) thin films were prepared using the spin-coating method onto Pt/Ti/SiO2/Si substrate by the metal organic decomposition. Crystallographic properties of BLT films were characterized as a function of annealing temperature. The effect of excess Bi content on the microstructure and ferroelectric properties was also investigated. X-ray diffraction (XRD) results show that predominant Bi4Ti3O12 phase can be obtained at 550 °C, while the films keep randomly oriented structure up to 750 °C. An increase in grain size of BLT films with increasing annealing temperature was observed by the field emission scanning electron microscopy (FE-SEM). The hysteresis loops of BLT films were found to be well defined for temperatures above 600 °C. The remanent polarization decreased when more than 10% of excess Bi has been used in the precursor solution. The films with both Bi deficiency and Bi excess over 10% in the BLT precursor solution annealed at 650 °C showed poor fatigue properties. This was attributed to the structure defects and to the presence of a secondary phase. The films prepared with the Bi content in excess of 10% and annealed at 650 °C exhibited an outstanding hysteresis behaviors with the remanent polarization (2Pr) of 25.66 as well as fatigue-free behavior up to 3.5×109 bipolar cycles.