Characteristics of Bismuth Layered SrBi₂Ta₂O₉ Thin-Film Capacitors and Comparison with Pb(Zr, Ti)O₃

Abstract

We have developed the series of thin-film bismuth layer structured ferroelectric (BLSF) materials such as SrBi 2 Ta 2 O 9 , SrBi 2 Nb 2 O 9 , SrBi 4 Ti 4 O 15 and their solid solutions using metallo-organic-decomposition (MOD) spin-on coating techniques. We found that SrBi 2 Ta 2 O 9 is one of the best potential candidate materials for ferroelectric nonvolatile memories. The SrBi 2 Ta 2 O 9 thin-film capacitor had the remanent polarization ( P r+ - P r- ) of 20 µ C/cm 2 , coercive field of 35 kV/cm and dielectric constant of 250. SrBi 2 Ta 2 O 9 thin film on platinum electrode has fatigue-free characteristics for up to 2×10 11 cycles without requiring any complicated electrode system such as conductive oxide. Moreover, SrBi 2 Ta 2 O 9 thin film has many advantages, e.g. , high signal/noise ratio of 8 at 1.2 V, low-voltage operation at as low as 1 V, long data-retention, little surface effect, superior imprint properties and low leakage current. We considered that these advantages are due to (1) less space charge and (2) the inherent domain motion.