Effect of Annealing Temperature on Electrical Properties of Ferroelectric Bi3.25La0.75Ti3O12 Capacitors

Abstract

Lanthanum-modified bismuth titanate (Bi3.25La0.75Ti3O12, BLT) thin films are fabricated on platinized Si wafers by the sol-gel method, and the effect of annealing temperatures ranging from 650°C to 800°C on the electrical properties of Pt/BLT/Pt capacitors are investigated. It is found that polarization and leakage current of BLT capacitors strongly depend on the annealing temperature although all the capacitors demonstrate very similar characteristics, except the value of polarization, in pulse-width dependence, retention, and fatigue. Remanent polarization increases with the increase of annealing temperature, and annealing temperature of 700°C can yield the largest remanent polarization, and then polarization decreases with increasing annealing temperature. For the 700°C annealed Pt/BLT/Pt capacitor, the remanent polarization 2Pr and the coercive field 2Ec, at an electric field of 226kV/cm, are 23.8μC/cm2 and 130kV/cm, respectively. Dielectric breakdown voltages of BLT films annealed at 750°C and 800°C are much lower than those annealed at 650°C and 700°C. At 100kV/cm, the leakage currents of BLT films prepared at 650°C and 700°C are only 1.5 × 10−6 A/cm2 and 8. 9 × 10−7 A/cm2, respectively. Moreover, all the Pt/BLT/Pt capacitors exhibit excellent retention properties after a cumulative time of 1 × 104 s and do not show any significant fatigue up to 1 × 1010 switching cycles at frequency of 1 MHz.