High speed deposition of high-quality ferrite films from aqueous solution at low temperatures (≤90 °C)

Abstract

We have plated polycrystalline CoxFe3−xO4 (x=0 and 0.43) films on PET and glass substrates at 80–90 °C in an aqueous solution by new three methods: (1) spraying, (2) spin coating, and (3) thin liquid-film methods. The reaction solution is (1) sprayed, (2) spin coated, and (3) flowed through a gap between the substrate and a glass plate, respectively, making a thin (5–400 μm) coating of the solution on the substrate. Since the solution flows off, the composition of the solution on the substrate does not significantly change during the plating, and the ferrite particles formed in the solution are washed away. This improves the film quality compared to previous methods. We have further improved the film quality by introducing CH3COO− buffer ions into the solution, and also by filtering the solution. By the thin liquid-film method, we have obtained maximum deposition rates of ∼160 and ∼300 Å/min by the spraying and the thin liquid-film methods, respectively. The films of Fe3O4 and CoxFe3–xO4 (x=0.43) plated by the thin liquid-film method exhibited a preferential texture of (100) and (111) planes, respectively, parallel to the surface. Both films had a columnar structure normal to the surface, but the magnetization lies in the surface plane.