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    Please use this identifier to cite or link to this item: http://tkuir.lib.tku.edu.tw:8080/dspace/handle/987654321/98414

    Title: Observation of the Origin of d0 Magnetism in ZnO Nanostructures Using X-ray-based Microscopic and Spectroscopic Techniques
    Authors: Singh, Shashi B.;Wang, Yu-Fu;Shao, Yu-Cheng;Lai, Hsuan-Yu;Hsieh, Shang-Hsien;Limaye, Mukta V.;Chuang, Chen-Hao;Hsueh, Hung-Chung;Wang, Hsaio-tsu;Chiou, Jau-Wern;Tsai, Hung-Ming;Pao, Chih-Wen;Chen, Chia-Hao;Lin, Hong-Ji;Lee, Jyh-Fu;Wu, Chun-Te;Wu, Jih-Jen;Pong, Way-Faung;Ohigashi, Takuji;Kosugi, Nobuhiro;Wang, Jian;Zhou, Jigang;Regier, Tom;Sham, Tsun-Kong
    Contributors: 淡江大學物理學系
    Keywords: d0 magnetism;nanostructures
    Date: 2014-07-01
    Issue Date: 2014-07-31 15:41:17 (UTC+8)
    Publisher: Cambridge: R S C Publications
    Abstract: Efforts have been made to elucidate the origin of d(0) magnetism in ZnO nanocactuses (NCs) and nanowires (NWs) using X-ray-based microscopic and spectroscopic techniques. The photoluminescence and O K-edge and Zn L3,2-edge X-ray-excited optical luminescence spectra showed that ZnO NCs contain more defects than NWs do and that in ZnO NCs, more defects are present at the O sites than at the Zn sites. Specifically, the results of O K-edge scanning transmission X-ray microscopy (STXM) and the corresponding X-ray-absorption near-edge structure (XANES) spectroscopy demonstrated that the impurity (non-stoichiometric) region in ZnO NCs contains a greater defect population than the thick region. The intensity of O K-edge STXM-XANES in the impurity region is more predominant in ZnO NCs than in NWs. The increase in the unoccupied (occupied) density of states at/above (at/below) the conduction-band minimum (valence-band maximum) or the Fermi level is related to the population of defects at the O sites, as revealed by comparing the ZnO NCs to the NWs. The results of O K-edge and Zn L3,2-edge X-ray magnetic circular dichroism demonstrated that the origin of magnetization is attributable to the O 2p orbitals rather than the Zn d orbitals. Further, the local density approximation (LDA) + U verified that vacancies in the form of dangling or unpaired 2p states (due to Zn vacancies) induced a significant local spin moment in the nearest-neighboring O atoms to the defect center, which was determined from the uneven local spin density by analyzing the partial density of states of O 2p in ZnO.
    Relation: Nanoscale 6(15), pp.9166-9176
    DOI: 10.1039/c4nr01961j
    Appears in Collections:[Graduate Institute & Department of Physics] Journal Article

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