AVS 51st International Symposium
    Magnetic Interfaces and Nanostructures Thursday Sessions
       Session MI-ThM

Paper MI-ThM8
Synthesis of Room-Temperature Ferromagnetic Materials by Ion Implantation: Transition-Metals-Doped TiO@sub 2@ (110) Rutile

Thursday, November 18, 2004, 10:40 am, Room 304A

Session: Magnetic Oxides and Half-Metallics
Presenter: V. Shutthanandan, Pacific Northwest National Laboratory
Authors: V. Shutthanandan, Pacific Northwest National Laboratory
S.T. Thevuthasan, Pacific Northwest National Laboratory
S.M. Heald, Pacific Northwest National Laboratory
T.C. Droubay, Pacific Northwest National Laboratory
M.H. Engelhard, Pacific Northwest National Laboratory
C.M. Wang, Pacific Northwest National Laboratory
D.E. McCready, Pacific Northwest National Laboratory
T.C. Kaspar, Pacific Northwest National Laboratory
S.A. Chambers, Pacific Northwest National Laboratory
P. Nachimuthu, Lawrence Berkeley National Laboratory
B.S. Mun, Lawrence Berkeley National Laboratory
Correspondent: Click to Email
There is growing interest in diluted magnetic semiconductors (DMS) in the emerging field of spintronics. It has recently been demonstrated that certain oxide semiconductors doped with magnetic transition metal elements show room-temperature ferromagnetism. In particular, titanium dioxide in both anatase and rutile phases appear to be among the most promising oxide semiconductors for DMS applications. In this study, we show that ferromagnetic transition metal doped TiO@sub 2@ (110) rutile single crystals can be successfully synthesized using ion implantation by carefully controlling implantation parameters such as temperature and ion fluence. Co, Cr, Ni and Fe ions with 100 keV energy were implanted at 875 K to 1075 K and an ion fluence of ~1.25x10@super 16@ ions/cm@super 2@. Vibrating sample magnetometer (VSM) measurements clearly show room temperature ferromagnetic responses with magnetic moments ranging from 0.30 to 0.70 µ @sub B@ /atom. X-ray photoelectron spectroscopy (XPS) depth profiling and Rutherford backscattering spectrometry (RBS) measurements reveal that most of the implanted dopants are uniformly distributed to a depth of ~300 nm with an average concentration of ~1 to 3 at%. K-edge x-ray absorption near edge spectra (XANES) obtained from the implants show that all of the implanted atoms are oxidized and that the formal oxidation is +2 for Co and Ni, +3 for Cr and a mixture of +2 and +3 for Fe. There is no evidence that the dopant is in the metallic state in these implanted samples. In addition, surface-sensitive total electron yield (TEY) and bulk-sensitive total florescence yield (TFY) obtained from the L-edge of Ti and implants and K-edge of O demonstrate that the structural environments in both surface and bulk regions of rutile TiO@sub 2@ are not significantly affected by the incorporation of implanted species.