Microstructure and growth of epitaxial nano-scale LaBaCo₂O_5.5+δislands on (La,Sr)(Al,Ta)O₃substrate

Epitaxial nano-scale LaBaCo₂O_5.5+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}_LBCOside surfaces and form on nano-sized {111}_Co3O4faceted Co₃O₄secondary 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 Co₃O₄secondary phase are determined. The atomic structure of the coherent interfaces between the Co₃O₄phase 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.