Oxygen pressure and Mn-doping effects on the structure and leakage current of Bi₆Ti₅TeO₂₂ thin film

Te ions existed as Te6+ in the Bi6 Ti5 Te O22 (BTT) film grown at 300°C under a high oxygen pressure (OP) of 80.0 Pa and contributed to the formation of the crystalline BTT phase after subsequent annealing at 600°C. However, for the BTT film grown under a low OP of 53.3 Pa (or 9.33 Pa), Te6+ ions, were converted to Te4+ ions, which induced the phase transition of the BTT phase to the pseudo- Bi4 Ti3 O12 and pseudo- Bi2 Ti2 O7 phases after annealing at 600°C. The leakage current density decreased with increasing OP during the growth due to the decreased number of oxygen vacancies. The breakdown voltage also improved with increasing OP during the deposition. The Mn ions introduced in the BTT films by Mn doping existed as Mn2+ or Mn4+ and acted as the acceptors. This Mn doping to 10 mol % also reduced the leakage current density and increased the breakdown voltage by decreasing the number of intrinsic oxygen vacancies.