Electrical properties and microstructures of all-perovskite-oxide capacitors (SrRuO 3/Ba xSr 1− xTiO 3/SrRuO 3)

Abstract

Single crystal epitaxial and polycrystalline thin film capacitors consisting entirely of perovskite oxides (SrRuO 3/Ba x Sr 1− x TiO 3 (20 nm)/SrRuO 3) were fabricated on SrTiO 3 and Si substrates by r.f. magnetron sputtering. The dielectric constants for single crystal epitaxial and polycrystalline capacitors were observed to be 681 and 274, respectively; this large difference in dielectric constants is suggested to be due to lattice distortion and grain boundaries. In spite of a thin thickness for Ba x Sr 1− x TiO 3 (20 nm), low leakage current densities for both capacitors (<1×10 −7 A cm −2 for a bias of ±1.2 V) were observed, which is suggested to be due to high lattice matching at the interface between dielectric and electrode. In the microstructure of the polycrystalline capacitor, Ba x Sr 1− x TiO 3 (BSTO) and SrRuO 3 (SRO) formed continuous columnar grains and showed epitaxial growth at the BSTO/SRO interface within each column; this microstructure was modeled as a `local epitaxial film' which was situated between single crystal epitaxial and polycrystalline films.