Atomic-Scale Structure and Properties of Thin Epitaxial SrRuO3 Films Grown on SrTiO3 (100) by Pulsed Laser Deposition

Transition metal oxides with perovskite structure exhibit a wide range of electrical properties. SrRuO3 (SRO), a perovskite oxide with high conductivity, finds applications as an electrode layer in ferroelectric devices and as a barrier layer in superconductor-normal metal-superconductor (SNS) Josephson junctions involving high Tc superconductors. Here we report on the structure and properties of thin SRO films on SrTiO3 (100) substrates grown by pulsed laser deposition. AFM investigations revealed that the SRO films exhibit island growth. The island size increases with thickness, and at a typical thickness of about 20 nm a connected network of islands is formed. The resistivity of the SRO films grown at different substrate temperatures (700 °C - 850 °C) exhibits metallic behavior with a ferromagnetic transition at 150 K. The films with typical thicknesses of 20 nm, grown at a substrate temperature of 775 °C exhibited the lowest resistivity of 200 μΩ-cm at 300 K, whereas the films grown at lower (700 °C) and higher (850 °C) temperatures showed a much higher resistivity at 300 K. By AFM and high resolution TEM investigations, this behavior is correlated with the atomicscale structure of the films. The film with the lowest room temperature resistivity showed an almost defect-free orthorhombic structure, whereas the film grown at 850 °C contained structural defects in high density, such as SrO-rich antiphase boundaries and twins located at the boundaries between the islands. The films grown at 700 °C showed a cubic perovskite structure, which is obviously the reason for their high resistivity.