Preparation and Electrical Properties of Highly (111)-Oriented (Na0.5Bi0.5) TiO3 Thin Films by a Sol-Gel Process

Sodium bismuth titanate, (Na0.5Bi0.5)TiO3 (NBT), thin films were grown on Pt/Ti/SiO2/Si substrates via a sol-gel process. The precursor solution for spin-coating was prepared from bismuth nitrate, sodium acetate, and titanium n-butoxide as starting materials, and acetic acid and methanol as solvents, and pervoskite NBT films with high (111)-orientation have been obtained. The Au/NBT/Pt thin film capacitor showed a hysteresis loop at an applied electric field of 200 kV/cm with remanent polarization (Pr) and coercive electric field (Ec) values of 20.9 µC/cm2 and 112 kV/cm, respectively. At 100 kHz, the dielectric constant and loss tan (delta)of the film were 171 and 0.024, respectively. The leakage current depended on the voltage polarity. When an electrical field ranges from 0 to 167 kV/cm and with the Pt electrode biased negatively, the NBT/Pt interface exhibits a Schottky emission characteristic. The Au/NBT interface forms an ohmic contact. The conduction current when the Au electrode is biased negatively shows space-charge-limited current (SCLC) behavior.