Studies of Ni and Co Doped Amorphous AlN for Magneto-Optical Applications
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1202-I05-06
Studies of Ni and Co Doped Amorphous AlN for Magneto-Optical Applications W. M. Jadwisienczak1, H. Tanaka1, M. E. Kordesch2, A. Khan3,4, S. Kaya1 and R. Vuppuluri1 1 2 3 4
School of EECS, Ohio University, Athens, Ohio, U.S.A. Department of Physics and Astronomy, Ohio University, Athens, OH, U.S.A. Department of Chemistry and Biochemistry, Ohio University, Athens, OH, U.S.A. Department of Physics, University of Peshawar, Peshawar, Pakistan.
ABSTRACT Magneto-optical properties of Ni- and Co-doped amorphous AlN thin films were investigated as a function of post grown annealing temperature using magneto-optical Kerr effect (MOKE) spectroscopy. The x-ray diffraction spectra confirmed that the as-grown material is amorphous and retained its morphology after thermal treatment; however the sample morphology strongly depends on the concentration of incorporated transition metals. We observed with help of transmission electron microscopy and atomic force microscopy that the films surface containing TMs with concentrations larger than ~10 at.% undergo morphological changes suggesting possible Ni and Co atom clustering. Significant enhancement of the polar Kerr rotation signal was observed for Ni- and Co-doped a-AlN materials annealed above 300 °C in nitrogen. The studied materials have shown strong magnetic isotropy in polar geometry whereas the MOKE measurements in longitudinal geometry did not show an explicit signal for the transition metals doped a-AlN studied. INTRODUCTION Transition metals (TM) doped group-III nitride semiconductors (III-Ns) are well known for their potential applications in spintronics [1]. The room-temperature magneto-optic Kerr effect in the magnetic semiconductor materials combines the magnetic and optical properties of the materials together, making them attractive for the development of magnetic recording media, as well as for multifunctional photo-magneto-electronics applications including sensors where the strong light-matter coupling is essential [2]. There are a number of reports about ferromagnetism in TM-doped III-Ns [3-6], respectively, although more work focused on the structural and magnetic properties of these materials is necessary before practical applications will become feasible. In spite of the difficulty and controversies surrounding the understanding of the origin of the magnetization in magnetic semiconductors, the formation of magnetic III-Ns has sparked widespread interest due to the possibility of making highly efficient spin injectors for spintronics. It is known that diluted magnetic semiconductors for practical applications require two essential features. One, Curie temperature must remain higher than room temperature; second, the basis should be on a typical semiconductor in which the carrier control technique is well established [3,4]. Among the most promising candidates for this task are some diluted ferromagnetic nitrides and oxides [3]. Nickel and Cobalt were already studied in polycrystalline and crystalline AlN materials and their magnetic properties we
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