Effect of excess Bi2O3 on the ferroelectric and dielectric properties of Bi3.25La0.75Ti3O12 thin films by RF sputtering method

Bi3.25La0.75Ti3O12 (BLT) thin films derived from different amounts of Bi2O3 excess content were fabricated on Pt/TiO2/SiO2/Si using RF-magnetron sputtering method. The effect of Bi2O3 excess content on the microstructure, ferroelectric and dielectric properties of the BLT films was investigated. The X-ray diffraction analysis reveals a layered perovskite structure phase without pyrochlore phase for all the BLT films. Appropriate amount of excess bismuth improves remnant polarization of the BLT film, while too much excess bismuth leads to a reduction in remnant polarization and an increase in coercive voltage. P–V loops of well-established squareness were observed for the BLT films derived from a moderate amount of Bi2O3 excess (7.5 mol%), where a remnant polarization (2Pr) of 25.26 μC/cm2 and coercive voltage (Vc) of 3.62 V were shown. A similar change in dielectric constant with the increasing of Bi2O3 excess content was also observed. Moreover, the BLT thin film derived from 7.5 mol% Bi2O3 excess shows the best fatigue resistance characteristics and about 8.1% polarization degradation after 1 × 109 read/write switching cycles.