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Room temperature ferromagnetism in Mn ion implanted epitaxial ZnO films

Epitaxial ZnO films of ∼450 nm thicknesses were grown by MOCVD on r‐sapphire and doped by implantation of 200 keV Mn ions to a dose of 5 × 1016 ions/cm2. The structural, chemical, and magnetic properties of the films were investigated with X‐ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), X‐ray absorption spectroscopy (XAS) and SQUID magnetometry. XRD and RBS show both Mn‐doped ZnO and pure ZnO epitaxial layers in the as‐implanted film, which is ferromagnetic at 5 K but nonmagnetic at room temperature. For the as‐implanted materials, only Mn2+ ions are observed with XAS. Post‐implantation annealing partially recovers the lattice damage and redistributes Mn into the entire ZnO film; in addition, Mn2+ ions are converted to a mixture of Mn3+ and Mn4+, and ferromagnetism is now observed above 300 K. Our results show that ion implantation is a viable route for achieving room temperature ferromagnetism in epitaxial ZnO films. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)