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

Abstract

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 degrees C, while the films keep randomly oriented structure up to 750 degrees 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 degrees 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 degrees 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 degrees C exhibited an outstanding hysteresis behaviors with the remanent polarization (2P(r)) of 25.66 as well as fatigue-free behavior up to 3.5 x 10(9) bipolar cycles. (c) 2004 Elsevier B.V. All rights reserved.