Effect of Anneal Conditions on Electrical Properties of Mn‐Doped (Na _0.85 K _0.15 ) _0.5 Bi _0.5 TiO ₃ Thin Films Prepared by Sol–Gel Method

Abstract

Mn‐doped (Na 0.85 K 0.15 ) 0.5 Bi 0.5 TiO 3 (NKBT‐Mn) thin films were fabricated on Pt(111)/Ti/SiO 2 /Si substrates via an aqueous sol–gel method and annealed at different temperatures from 550° to 800°C. Two different crystallization processes, i.e., single crystallization and multiple crystallizations, were used. The structures of the films were analyzed using X‐ray diffraction, which shows that the NKBT‐Mn thin film prepared by multiple crystallizations crystallize into the pure perovskite phase, while pyrochlore phase formed in the film prepared by the single crystallization. Ferroelectric and dielectric properties of NKBT‐Mn thin films are quite dependent on the anneal temperature. The P r value was a maximum for the 700 o C‐annealed thin film and decreased with both decreasing and increasing anneal temperature. The NKBT‐Mn thin film annealed at 700°C had the largest ɛ r of 426 and the lowest tan δ of 0.061. At the same time, the temperature‐dependent ferroelectric property was also investigated from room temperature to −150°C. It is found that P r of the film sample increases as temperature decreases, which can be well explained by a temperature‐dependent charged carriers–domain wall interaction. Current density measurement indicates that the change in morphology with increasing anneal temperature and the volatility of Bi and Na/K at high temperature may responsible for the change in leakage current density and the NKBT‐Mn thin film annealed at 700°C has the lowest leakage current of 7.6 × 10 −5 A/cm 2 .