Temperature-dependent leakage current behavior of epitaxial Bi _0.5Na_0.5TiO₃-based thin films made by pulsed laser deposition

This paper discusses the electrical conduction mechanisms in a 0.88 Bi _0.5Na_0.5TiO₃-0.08 Bi_0.5K _0.5TiO₃-0.04 BaTiO₃ thin film in the temperature range of 200-350 K. The film was deposited on a SrRuO ₃/SrTiO₃ substrate by pulsed laser deposition technique. At all measurement temperatures, the leakage current behavior of the film matched well with the Lampert's triangle bounded by three straight lines of different slopes. The relative location of the triangle sides varied with temperature due to its effect on the density of charge carriers and un-filled traps. At low electric fields, the ohmic conduction governed the leakage mechanism. The calculated activation energy of the trap is 0.19 eV implying the presence of shallow traps in the film. With increasing the applied field, an abrupt increase in the leakage current was observed. This was attributed to a trap-filling process by the injected carriers. At sufficiently high electric fields, the leakage current obeyed the Child's trap-free square law suggesting the space charge limited current was the dominant mechanism.