Microstructure and Crystallization Behavior of Fe-M-O (M=Hf, Zr) Films with High Resistivity

The microstructure, crystallization behavior and electrical resistivity of different Fe-M-O (M=Hf,Zr) films prepared by the rf magnetron sputtering technique were investigated. In the as-deposited state, the structures of Fe-M-O films with a solute content of 13 to 22.7 at% Hf and 15 to 38 at% O, or of 5 to 13 at% Zr and 8 to 30 at% O, were found to consist of a bec phase with grain diameters below 10 nm and an amorphous phase containing larger amounts of M and O. The film crystallizes in two stages, corresponding to the precipitation and grain growth of the bec phase and of oxides, respectively. The amorphous phase region expanded with increasing M content, and the electrical resistivity rapidly increased, reaching 1860 μΩm for an FeHf_18.2O_35.6 film with a structure composed of a large amorphous phase region and a small bec phase region.