Preparation of fatigue-free SrBi2Ta2O9 thin films by r.f. magnetron sputtering and their ferroelectric properties

Abstract

Fatigue-free bismuth-layered SrBi₂Ta₂O₉ (SBT) films were deposited on Pt/Ti/SiO₂/Si substrates by r.f. magnetron sputtering at room temperature. The variation of structure and electrical properties were studied as a function of annealing temperatures from 750–850 °C. The films annealed at 800 °C had a composition ratio of Sr:Br:Ta = 0.7:2.0:2.0. X-ray photoelectron spectroscopy signals of bismuth show an oxygen-deficient state within the SBT films. The films annealed at 800 °C have a thickness of 200 nm and a relatively dense microstructure. The remanent polarization (2P _r), and the coercive field (2E _c), obtained for the SIBT films, were 9.1 μC cm⁻² and 85 kV cm⁻¹ at an applied voltage of 3 V, respectively. The films showed fatigue-free characteristics up to 10¹⁰ cycles under 5 V bipolar square pulses. The leakage current density was about 7 × 10⁻⁷ A cm⁻² at 150 kV cm⁻¹. The SBT films prepared by r.f. magnetron sputtering were attractive for application to non-volatile memories.