Three-dimensional heteroepitaxy in self-assembled BaTiO3–CoFe2O4 nanostructures

Self-assembled BaTiO3–CoFe2O4 complex oxide nanostructures have been synthesized by pulsed laser deposition. A single ceramic target with a molar ratio of 0.62BaTiO3–0.38CoFe2O4 was used. Spinel CoFe2O4 and perovskite BaTiO3 phases spontaneously separated during heteroepitaxial growth on a single-crystal SrTiO3(001) substrate. The nanostructures are epitaxial in-plane as well as out-of-plane, with CoFe2O4 nanopillar arrays embedded in a BaTiO3 matrix. The CoFe2O4 nanopillars have uniform size and spacing and nearly circular cross section. As the substrate temperature increases from 750 to 950°C, the average diameter of the pillars increases from ∼9 to ∼70nm.