Effects of oxygen pressure and Mn-doping on the electrical and dielectric properties of Bi₅Nb₃O₁₅ thin film grown by pulsed laser deposition

Bi₅Nb₃O₁₅ (B₅N₃) thin films grown at temperatures above 500 °C developed a crystalline B ₅N₃ phase that decomposed into a BiNbO₄ phase in the film grown at 700 °C, probably due to Bi₂O₃ evaporation. The leakage current density of the B₅N₃ film grown at 200 °C under an oxygen pressure (OP) of 100 mTorr was high at approximately 6.3 × 10^-7 A cm^-2 at 0.2 MV cm ^-1, with a small breakdown field of 0.24 MV cm^-1 due to the presence of intrinsic oxygen vacancies. The electrical properties of the B₅N₃ films improved with increasing OP during the growth but the dielectric constant (ε_r) decreased. The Mn-doping also improved the electrical properties of the B₅N₃ films grown under low OP by producing doubly ionized oxygen vacancies, which decreased the number of the intrinsic oxygen vacancies. Furthermore, the Mn-doping increased the ε_r value of the B₅N₃ film, confirming the effectiveness of such doping in improving both the electrical and the dielectric properties of the B₅N₃ film. In particular, the 5.0 mol% Mn-doped B₅N₃ film grown at 200 °C under an OP of 100 mTorr exhibited a low leakage current density of 7.9 × 10 ^-8 A cm^-2 at 0.2 MV cm^-1 and a large breakdown field of 0.4 MV cm^-1 with a high ε_r of 64.