A new SrBi4Ti4O15/CaBi4Ti4O15 thin-film capacitor for excellent electric stability

SrBi₄Ti₄O₁₅ (SBTi) and CaBi₄Ti₄O₁₅ (CBTi) dielectric films of bismuth layered-structure dielectrics (BLSD) are prepared on Pt(100) film for constructing stacked-type dielectric capacitors; it is observed that they are c-axis single-oriented crystalline films. Compared with the perovskite barium titanate family of (Ba,Sr)TiO₃ (BST), it is observed that the SBTi film keeps a low leakage of 10^-7 A/cm² at 250 kV/ cm, which is smaller by an order of magnitude than the BST film, even with thinner SBTi film. The temperature coefficient of capacitance (TCC) of the SBTi or CBTi film is about 100 to 250 ppm/K and is much smaller than that of the perovskite BST film. Because the SBTi and CBTi films have opposite polarities of TCC in this experiment, they are expected to cancel out the temperature dependence in the SBTi/CBTi composite capacitor. These results indicate that the BLSD films of SBTi and CBTi are effective for application in high-temperature and high-permittivity capacitors with the practical barium perovskite oxide family.