Hitoshi Shinno and Kazuo Saito
National Research Institute for Metals, Tsukuba
Nitrogen ions were implanted into r.f. sputtered Fe thin films to synthesize Fe16N2 iron nitride. When the film thickness was 250 nm, Fe16N2 was formed in the Fe films during nitrogen ion implantation without postannealing. From the intensity ratios of X-ray diffraction peaks, the maximum volume fraction of Fe16N2+α′-martensite was estimated to be about 60%. The volume fraction of Fe16N2 of this sample did not change after postannealing at 423 K for 3.6 ks.
When the film thickness was 50 nm, Fe16N2 was not formed during the ion implantation, but the volume fraction of α′-martensite exceeded 90%. Implanted nitrogens escaped from the surface of the as-implanted specimen during the postannealing, decreasing the volume fraction of synthesized Fe16N2. However, Cu coating on the ion implanted specimen prevented the nitrogen escape and increased the volume fraction of Fe16N2 markedly.
(Received November 22, 1995)
Fe16N2, ion implantation, saturation magnetization, thin film, X-ray diffraction, α′-martensite
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