Structural and electrical properties of (1-x)Bi₅Nb₃O₁₅-xBi₄Ti₃O₁₂ ceramics and 0.96Bi₅Nb₃O₁₅-0.04Bi₄Ti₃O₁₂ thin films grown by pulsed laser deposition

A 0.96Bi₅Nb₃O₁₅-0.04Bi₄Ti₃O₁₂ (0.96B₅N₃-0.04B₄T₃) ceramic showed a high dielectric constant (k) of 314, probably due to the increased dipole moment caused by the replacement of Nb⁵⁺ ions by Ti⁴⁺ ions. The 0.96B₅N₃-0.04B₄T₃ films were well formed on the Pt/Ti/SiO₂/Si substrate. Films grown at temperatures lower than 400°C had an amorphous phase but small Bi₃NbO₇ crystals were considered to have been formed in these films. The film grown at 300°C exhibited a high k value of 83 with a low dielectric loss of 0.5%. The leakage current density of the film grown at low oxygen pressure (OP) was high and decreased with increasing OP to a minimum at an OP of 200 mTorr, after which it increased with further increase in OP. This variation of the leakage current density with OP was explained by the existence of oxygen vacancies and interstitial oxygen ions in the film. The 0.96B₅N₃-0.04B₄T₃ film grown under 200 mTorr OP exhibited a high k value of 83, a low leakage current density of 8 × 10^-8A/cm² at 0.3MV/cm and a high breakdown field of 0.4MV/cm.