Crystallization and improvement of electrical properties of Bi ₅Nb₃O₁₅ thin films grown at low temperature

Amorphous Bi₅Nb₃O₁₅ (B₅N ₃) phase was formed for the films grown at350°C under low oxygen pressures (OPs) (≤ 200 mTorr). However, when OP exceeded 400 mTorr, crystalline Bi₃NbO₇ (B₃N) phase, which is a low temperature transient phase of the crystalline B₅N₃ phase, was formed even at 350 °C. The dielectric constant (k) increased with increasing OP due to the formation of the crystalline B₃N phase. The leakage current density increased with increasing OP, due to the increased surface roughness of the film. Presence of the intrinsic oxygen vacancies was also responsible for the increased leakage current density. Mn-doping improved the electrical properties of the films by producing the doubly ionized, extrinsic oxygen vacancies which reduced the number of the intrinsic oxygen vacancies. Mn-doping also considerably increased the k value of the film to a maximum of 108 for the 5.0 mol % Mn-doped film grown at 350°C.