Structure and voltage dependence of ferroelectric properties of SrBi2Ta2O9 thin films

Abstract

Polycrystalline SrBi2Ta2O9 (SBT) ferroelectric thin films were synthesized on Pt/Ti/SiO2/Si substrates by the metalorganic decomposition technique. The SBT crystalline phase appeared at 550 °C, completely crystallized at 650 °C, and little pyrochlore phase was observed in the x-ray diffraction patterns. The grains, which are rodlike, increased from about 50 to 200 nm in diameter with increasing annealing temperature from 550 to 800 °C. Typically, the SBT thin film annealed at 750 °C had Pr=8.8 μC/cm2 and Ec=29.3 kV/cm at applied voltage of 5 V, and the hysteresis loops become saturated with an increase of the maximum applied voltage. The fatigue and retention characteristics of SBT thin films dependence on applied voltage and frequency have also been investigated. It revealed that the fatigue endurance at a higher frequency and a higher applied voltage could be better than that at a lower frequency and a lower applied voltage. The retention properties of the SBT thin films are quite good over a range of 1–10 000 S, and the influence of applied voltage and bias voltage is not obvious.