Electrical properties of all-perovskite oxide (SrRuO3/BaxSr1-xTiO3/SrRuO3) capacitors

Thin film capacitors consisting totally of perovskite oxides (SrRuO3/BaxSr1-xTiO3(20 nm)/SrRuO3) were fabricated on Si and SrTiO3 substrates by rf magnetron sputtering. The dielectric constants for polycrystalline and single-crystal epitaxial films were observed to be 274 and 681, respectively. The lowest SiO2 equivalent thickness for the single-crystal epitaxial capacitor was 0.11 nm. The leakage current density was less than 1 x 10(-7) A/cm(2) for a bias of +/-1.2V. The electrical properties of all-perovskite oxide capacitors were compared with those of samples with Pt top electrodes, and large differences in the values of the dielectric constant were observed. These are explained in terms of differences in the interface between the dielectric and the top electrode and the possible existence of a low-epsilon layer at the interface between the Pt top electrode and BaxSr1-xTiO3. In addition, the origin of the large difference in the dielectric constants for polycrystalline and single-crystal epitaxial capacitors are discussed in terms of the lattice distortion in BaxSr1-xTiO3.