Nanocomposites of metallic copper and spinel ferrite films: Growth and self-assembly of copper particles

Nanocomposites of metallic copper and iron oxides films have been prepared by RF-sputtering of pure CuFeO2 delafossite target. The films are made of copper and spinel ferrite crystallites of less than 10 nm in diameter. The content of metallic copper and the ferrite composition depend on the sputtering conditions. For the shortest substrate-target distances, films are made of copper and copper substituted magnetite with low copper content. The formation of the metallic and spinel phases is due to the loss of a small quantity of oxygen during sputtering. When annealed under inert atmosphere, nanometric copper particles located in the upper part of the film, move on the surface and grow due to coalescence phenomena. The particle motion can be stopped by small grooves allowing the self-assembly of copper particles.