Electrical properties of Na0.5Bi0.5TiO3 thin films deposited on sitall substrates

We report some special features of Na0.5Bi0.5TiO3 (NBT) thin films growth process, as well as structural and electrical properties of these films. The films were grown on Pt/sitall substrates by high-frequency (13.56 MHz) magnetron deposition method. To crystallize the films the NBT/Pt/sitall structure was annealed at a temperature around 500 degrees C divided by 700 degrees C in air. Results of X-ray diffraction showed that annealing at 700 degrees C led to the crystallization of the NBT films in the perovskite phase with minor inclusions of the pyrochlore phase. Temperature dependences of dielectric hysteresis loops (P-E) and current density-electrical field (J-E) characteristics were investigated. A tendency of narrowing of the hysteresis loops with an increase of the temperature to 180 degrees C was detected, which can be probably associated with the features of the diffuse rhombohedral/tetragonal phase transition. The remanent polarization (P-r) and the coercive field (E-c) values measured at room temperature were 9 mu C/cm(2) and 40 kV/cm, respectively. It was found that with an increase of the temperature the leakage currents increased in the entire investigated range of applied electrical fields. Charge transfer mechanisms responsible for the leakage currents in NBT thin films are discussed.