A three component self-assembled epitaxial nanocomposite thin film

A self-assembled three phase epitaxial nanocomposite film is grown consisting of ≈3 nm diameter fcc metallic Cu nanorods within square prismatic SrO rocksalt nanopillars in a Sr(Ti,Cu)O_3-δ perovskite matrix. Each phase has an epitaxial relation to the others. The core-shell-matrix structures are grown on SrTiO₃ substrates and can also be integrated onto Si using a thin SrTiO₃ buffer. The structure is made by pulsed laser deposition in vacuum from a SrTi_0.75Cu_0.25O₃ target, and formed as a result of the limited solubility of Cu in the perovskite matrix. Wet etching removes the 3 nm diameter Cu nanowires leaving porous SrO pillars. The three-phase nanocomposite film is used as a substrate for growing a second epitaxial nanocomposite consisting of CoFe₂O₄ spinel pillars in a BiFeO₃ perovskite matrix, producing dramatic effects on the structure and magnetic properties of the CoFe₂O₄. This three-phase vertical nanocomposite provides a complement to the well-known two-phase nanocomposites, and may offer a combination of properties of three different materials as well as additional avenues for strain-mediated coupling within a single film. nc-STCu films are grown in vacuum on Nb-doped (001) STO substrate after etching in ammonium hydroxide for 3 h. Metallic copper rods with ≈3 nm diameter grow in the center of the SrO nanorods in a perovskite matrix, and etching of the Cu by ammonium hydroxide creates uniformly sized nanopores.