Improvement of the electrical properties of TiO2-doped Bi5Nb3O15 thin films by the addition of MnO2

The leakage current density of a 1.0 mol% TiO2-doped Bi5Nb3O15 (TB5N3) film was high, and the breakdown electric field was low. This could be attributed to the presence of intrinsic oxygen vacancies and free electrons. The electrical properties of the TB5N3 film improved upon the addition of MnO2 because of the formation of extrinsic oxygen vacancies, which caused the number of intrinsic oxygen vacancies to decrease in order to maintain the equilibrium concentration of oxygen vacancies in the film. However, the electric properties degraded when the MnO2 content exceeded 15.0 mol% because of the formation of interstitial oxygen ions and holes. The dielectric constant (ɛr) of the TB5N3 film slightly decreased upon the addition of a small amount of MnO2. The TB5N3 film with 15.0 mol% MnO2, which exhibited a small leakage current density of 2.5 × 10−11 A/cm2 at 0.15 MV/cm and a high breakdown electric field of 0.47 MV/cm, still maintained a large ɛr of 118 with a small loss tangent of 2.0% at 100.0 kHz.