⁵⁶Fe⁺-ion implantation effects in Al₂O₃

Single and polycrystalline Al₂O₃ were implanted at room temperature with 60 keV ⁵⁶Fe⁺ ions with the dose range from 2.0 × 10¹⁶ up to 1.2 × 10¹⁷ ions/cm² using a 200 keV ion implanter. ⁵⁶Fe⁺-ion implantation effects in Al₂O₃ have been studied directly after by using four complementary techniques: Vibrating Sample Magnetometer (VSM), Rutherford Backscattering Spectroscopy (RBS), Grazing-angle X-ray Diffraction (GXRD) and X-ray Photoelectron Spectroscopy (XPS). The specimens implanted with above 6.5 × 10¹⁶ Fe⁺/cm² showed the behavior of paramagnetism or ferromagnetism which depend upon the ion dose or the size of α-Fe particles precipitated inside Al₂O₃ regardless of the crystallinity. The precipitation of α-Fe has been confirmed by the grazing-angle X-ray diffraction. From X-ray diffraction line broadening, it has been confirmed that the size of α-Fe particles in the single Al₂O₃ monotonically increases from 6.0 to 10.8 nm with the variation of the ion dose. The single Al₂O₃ implanted with Fe⁺ ions has had larger effective magneton number and the coercivity than those of polycrystalline Al₂O₃. The difference in the effective magneton number and the coercivity with the crystallinity is due to the differences in Fe depth profiles in the implanted layers. From XPS depth profiles, the relative ratio of metallic Fe is increased according to the increase of Fe concentration regardless of the crystallinity but oxide states of Fe were nearly constant throughout the depth profiles.