title: Observation of the origin of d0 magnetism in ZnO nanostructures using X-ray-based microscopic and spectroscopic techniques.
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.
authors: Department of Physics, Tamkang University, Tamsui 251, Taiwan. hchsueh@mail.tku.edu.tw jwchiou@nuk.edu.tw wfpong@mail.tku.edu.tw.
authors: Shashi B
authors: SB
authors: Singh
authors: Yu-Fu
authors: YF
authors: Wang
authors: Yu-Cheng
authors: YC
authors: Shao
authors: Hsuan-Yu
authors: HY
authors: Lai
authors: Shang-Hsien
authors: SH
authors: Hsieh
authors: Mukta V
authors: MV
authors: Limaye
authors: Chen-Hao
authors: CH
authors: Chuang
authors: Hung-Chung
authors: HC
authors: Hsueh
authors: Hsaiotsu
authors: H
authors: Wang
authors: Jau-Wern
authors: JW
authors: Chiou
authors: Hung-Ming
authors: HM
authors: Tsai
authors: Chih-Wen
authors: CW
authors: Pao
authors: Chia-Hao
authors: CH
authors: Chen
authors: Hong-Ji
authors: HJ
authors: Lin
authors: Jyh-Fu
authors: JF
authors: Lee
authors: Chun-Te
authors: CT
authors: Wu
authors: Jih-Jen
authors: JJ
authors: Wu
authors: Way-Faung
authors: WF
authors: Pong
authors: Takuji
authors: T
authors: Ohigashi
authors: Nobuhiro
authors: N
authors: Kosugi
authors: Jian
authors: J
authors: Wang
authors: Jigang
authors: J
authors: Zhou
authors: Tom
authors: T
authors: Regier
authors: Tsun-Kong
authors: TK
authors: Sham
mesh_terms: D005583:Fourier Analysis; D049449:Luminescence; D008280:Magnetics; D049329:Nanostructures; D036103:Nanotechnology / Q000379:methods*; D053770:Nanowires; D010100:Oxygen / Q000737:chemistry; D013053:Spectrophotometry; D013499:Surface Properties; D013696:Temperature; D017971:Tin Compounds / Q000737:chemistry; D056928:X-Ray Absorption Spectroscopy; D014965:X-Rays; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D017971:Tin Compounds; C045358:stannic oxide; D010100:Oxygen; D015034:Zinc Oxide