The preparation of a fatigue-free Bi ₄Ti ₃O ₁₂ thin film with controlling Bi-excess using sol-gel coating

A polycrystallinc Bi ₄Ti ₃O ₁₂ (BIT) thin film of ∼150 nm was fabricated by sol-gel process on Pt/Ti/SiO ₂/Si substrate. We observed that excess Bi concentration for precursor could influence the microstructure of the BIT film and thereby change the fatigue behavior. A high fatigue endurance of the BIT thin film was obtained, when the Bi excess was 1.0 mole %. This film exhibited enhanced a(b)-axis orientation and highly smooth surface consisted of grains of ∼30 nm in size. The remanent polarization and the coercive field were 8 μC/cm ² and 129 kV/cm at 8 V, respectively. The leakage current density was ∼1.5 × 10 ^-7 A/cm ² at 4.5 V. An excellent fatigue endurance was observed up to 1 × 10 ¹⁰ switching cycles.