Ferroelectric properties of neodymium-doped Bi4Ti3O12 thin films crystallized in different environments

Neodymium (Nd)-doped Bi4Ti3O12 (Bi3.15Nd0.85Ti3O12, BNT) ferroelectric films have been deposited on Pt/Ti/SiO2/Si substrates by a sol-gel process and crystallized in nitrogen, air and oxygen environments, respectively. The crystallization environment was found to be important in determining the crystallization and ferroelectric properties of the BNT films. The film crystallized in nitrogen at a relatively low temperature of 650 °C, and exhibits excellent crystallinity and ferroelectricity with a remanent polarization of 2Pr=63.6 μC/cm2, a coercive field of 130 kV/cm and a fatigue-free characteristic. While the films annealed in air and oxygen, they did not show good crystallinity and ferroelectricity until they were annealed at 710 and 730 °C, respectively. A correlation between the remanent polarization and dielectric constants of the BNT films has been observed.