Structural and electrical characterization of SrBi2Nb2O9 thin films deposited on YBa2Cu3O7−δ and Nb doped SrTiO3

We have investigated the crystal structure and the ferroelectric properties of SrBi2Nb2O9 (SBN) thin films with YBa2Cu3O7−δ (YBCO) as the bottom and Au as the top electrode. Epitaxial heterostructures of YBCO and SBN were prepared by dc and rf sputtering, respectively, on SrTiO3 substrates. In a second layout we used a semiconducting Nb doped (0.05 wt % Nb) SrTiO3 (N-STO) substrate as the bottom electrode. The crystal structure of the films was characterized by x-ray diffraction. Since the SBN films exhibit a perfect c-axis oriented growth without the (115) phase the hysteresis loop measurements do not indicate ferroelectric behavior of the SBN films. The diode with a N-STO bottom electrode reveals, for a positive and negative applied voltage, a depletion and accumulation of the carrier density, respectively. The time dependent polarization and depolarization current can be described by a power law (Curie-von Schweidler). The conductivity as a function of applied voltage can be explained by the Schottky effect.