Effect of excess bismuth on the microstructures and electrical properties of strontium bismuth tantalate (SBT) thin films

Abstract

Strontium bismuth tantalate (SBT) films with excess Bi contents were prepared on Pt/TiO2/SiO2/Si substrates by a metallorganic decomposition technique. Effect of excess Bi contents on the microstructure and electrical properties were investigated. A predominant layered perovskite structure could be formed when an excess Bi less than 30% was added. For films above 30% excess of Bi, secondary phases occurred. The remnant polarization and dielectric constant decreased with excess Bi content. This was attributed to a smaller grain size and the presence of secondary phases. The leakage current characteristics were also examined. Space charge limited mechanism was observed in SBT films. In summary, 10% excess Bi was found to be the optimum composition with respect to grain size, morphology, and electrical properties.