Improving the Properties of Sol–Gel Deposition SrBi₄Ti₄O₁₅ Thin Films by Post-annealing Process

In this study, the characteristics of the SrBi₄Ti₄O₁₅ (SBT) thin films were investigated by sol–gel method. Bi(NO₃)₃ and SrCO₃ were mixed with the ethylene glycol and acetic acid at 120 °C. After that, the titanium (IV) isopropoxide was added and mixed, and then the sol–gel precursor formula SrBi₄Ti₄O₁₅+4 wt% Bi₂O₃ (SBT) was obtained. After baking at 350 °C for 10min, the one-layer SBT thin films were obtained. The spin coating and baking process were repeated twice for the two-layer SBT thin films. After deposition, the SBT thin films were annealed in a conventional furnace (CTA) at 600, 700, and 800 °C for 60 min in O₂ atmosphere. The cross sections and the surface morphologies of SBT thin films were investigated by using FE-SEM, and the crystalline structures were characterized by XRD patterns. It was found that the grain sizes increased and the pores decreased with rising CTA temperature. The effects of annealing temperature on the electrical properties of SBT thin films were also recorded and analyzed, including the capacitance–voltage curves and the leakage current density–electric field curves.