Tuning the size and density of faceted Co3O4 nanoparticles in LaBaCo2O5.5+δ epitaxial thin films by strain engineering

Abstract

Both LaBaCo₂O_5.5+δ (LBCO) thin films and Co₃O₄ nanocrystals have potential applications in clean energy storage and ethanol gas detection. Herein, we report that the composite films of LaBaCo₂O_5.5+δ (LBCO) and {111} faceted Co₃O₄ nanoparticles were fabricated on (La,Sr)(Al,Ta)O₃ (LSAT) and SrTiO₃ (STO) substrates by magnetron sputtering deposition. The LBCO films revealed an epitaxial growth on both substrates with atomically sharp interfaces and a cubic-on-cubic orientation relationship. The Co₃O₄ particles were found to form at a very early stage of the film deposition and have the orientation relationship of [100]_Co3O4//[100]_LBCO and (100)_Co3O4//(100)_LBCO with the LBCO film matrix. It was found that the size and density of the Co₃O₄ particles can be tuned using different substrates, which induces different strains in the films. By means of high-resolution scanning transmission electron microscopy, the 3-dimensional morphology of the Co₃O₄ particles was illustrated. The formation and growth of the Co₃O₄ particles are discussed with respect to the strains of the films induced from the substrates.