Microstructure of epitaxial SrRuO3 thin films on MgO substrates

SrRuO3 thin films have been grown on singular (1 0 0) MgO substrates using pulsed laser deposition (PLD) in 30 Pa oxygen ambient and at a temperature of 400–700 8C. Ex situ reflection high-energy electron diffraction (RHEED) as well as X-ray diffraction (XRD) u/2u scan indicated that the films deposited above 650 8C were well crystallized though they had a rough surface as shown by atom force microscopy (AFM). XRD F scans revealed that these films were composed of all three different types of orientation domains, which was further confirmed by the RHEED patterns. The heteroepitaxial relationship between SrRuO3 and MgO was found to be [1 1 0] SRO//[1 0 0] MgO and 458-rotated cube-on-cube [0 0 1] SRO//[1 0 0] MgO. These domain structures and surface morphology are similar to that of ever-reported SrRuO3 thin films deposited on the (0 0 1) LaAlO3 substrates, and different from those deposited on (0 0 1) SrTiO3 substrates that have an atomically flat surface and are composed of only the [1 1 0]-type domains. The reason for this difference was ascribed to the effect of lattice mismatch across the film/substrate interface. The room temperature resistivity of SrRuO3 films fabricated at 700 8C was 300 mV cm. Therefore, epitaxial SrRuO3 films on MgO substrate could serve as a promising candidate of electrode materials for the fabrication of ferroelectric or dielectric films.