Structural and ferromagnetic properties of Cu-doped GaN
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R. Ernib) Department of Chemical Engineering and Materials Science, University of California at Davis, Davis, California 95616
Amita Gupta Department of Physics, Portland State University, Portland, Oregon 97207-0751; Department of Materials Science, Tmfy-MSE, The Royal Institute of Technology, SE 100 44 Stockholm, Sweden; and National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, California 94720
C. Li Department of Physics, Portland State University, Portland, Oregon 97207-0751; and Oregon Nanoscience and Microtechnologies Institute (ONAMI)
F.J. Owens Army Armament Research, Development and Engineering Center, Picatinny, New Jersey 07896; and Department of Physics, Hunter College, City University of New York, New York 10024
K.V. Rao Department of Materials Science, Tmfy-MSE, The Royal Institute of Technology, SE 100 44 Stockholm, Sweden
N.D. Browningc) Department of Chemical Engineering and Materials Science, University of California at Davis, Davis, California 95616; and National Center for Electron Microscopy, Lawrence Berkeley National Laboratory, Berkeley, California 94720
P. Moeck Department of Physics, Portland State University, Portland, Oregon 97207-0751 and Oregon Nanoscience and Microtechnologies Institute (ONAMI) (Received 24 October 2006; accepted 15 February 2007)
The wurtzite polymorph of GaN was calcined with CuO in flowing nitrogen. As a result of this processing, both superconducting quantum interference device magnetometry and ferromagnetic resonance studies showed ferromagnetism in these samples at room temperature. These magnetic results are qualitatively consistent with very recent first-principle calculations [Wu et al., Appl. Phys. Lett. 89, 062505 (2006)] that predict ferromagnetism in Cu-doped GaN. We focus in this paper on analyzing changes in the GaN atomic and electronic structure due to calcination with CuO using multiple analytical methods. Quantitative powder x-ray diffraction (XRD) showed changes in the lattice constants of the GaN due to the incorporation of copper (and possibly oxygen). Energy-dispersive x-ray spectroscopy proved the incorporation of copper into the GaN crystal structure. Electron-gun monochromated electron energy loss spectroscopy showed CuO calcinations-induced GaN band gap changes and indicated changes in the atomic arrangements due to the calcination process. The fine structure of the N K-edge showed differences in the peak ratios with respect to higher nominal CuO contents, corresponding to an increase in the c-lattice constant as confirmed by XRD. a)
Address all correspondence to this author. e-mail: [email protected] b) Present address: EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium c) Present address: Materials Science and Technology Division, Chemistry and Materials Science Directorate, Lawrence Livermore National Laboratory, Livermore, CA 94550 DOI: 10.1557/JMR.2007.0168 1396 J. Mater. Res., Vol. 22, No. 5, May 2007 http://journals.cambridge.org Downloaded: 15 Mar 2015
I. INTRODUCTIO
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