Microstructure and growth of epitaxial nano-scale LaBaCo2O5.5+δ islands on (La,Sr)(Al,Ta)O3 substrate

Epitaxial nano-scale LaBaCo2O5.5+δ (LBCO) islands are prepared on (La,Sr)(Al,Ta)O3 (LSAT) substrates by pulsed laser deposition technique. The microstructure of these islands is investigated by aberration-corrected (scanning) transmission electron microscopy. These islands exhibit morphologies of truncated octahedron with {111}LBCO side surfaces and form on nano-sized {111}Co3O4 faceted Co3O4 secondary phase that grows directly on the substrate. The crystallographic orientation relationships between the LBCO film and the LSAT substrate, as well as between the LBCO film and the Co3O4 secondary phase are determined. The atomic structure of the coherent interfaces between the Co3O4 phase and the LBCO islands is revealed by the atomic-resolution high-angle annular dark field images. Based on the obtained structural results, the growth mechanism of the islands is proposed and discussed.