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.[[notice]]補正完畢[[incitationindex]]SCI[[booktype]]紙本[[booktype]]電子

Redactable Signatures for Signed CDA Documents

[[abstract]]The Clinical Document Architecture, introduced by Health Level Seven, is a XML-based standard intending to specify the encoding, structure, and semantics of clinical documents for exchange. Since the clinical document is in XML form, its authenticity and integrity could be guaranteed by the use of the XML signature published by W3C. While a clinical document wants to conceal some personal or private information, the document needs to be redacted. It makes the signed signature of the original clinical document not be verified. The redactable signature is thus proposed to enable verification for the redacted document. Only a little research does the implementation of the redactable signature, and there still not exists an appropriate scheme for the clinical document. This paper will investigate the existing web-technologies and find a compact and applicable model to implement a suitable redactable signature for the clinical document viewer.[[notice]]補正完畢[[incitationindex]]SC

Electronic and Optical Properties of Silicon Carbide Nanostructures

[[abstract]]The electronic and optical properties of quasi-one-dimensional single-walled zigzag/armchair silicon-carbide nantotubes (SiC-NTs) as well as a two-dimensional SiC monolayer are investigated by ab initio methods. In order to elucidate many-electron effects on SiC nanosystems, we apply the ab initio many-body Green’s function approach to calculate the quasiparticle and optical properties of SiC nanostructures. The significant band gap correction, more than 1 eV, to the Kohn-Sham gap of density functional theory within the local density approximation of semiconducting SiC-NTs and a SiC monolayer is mainly due to the many-electron interaction effect, which is included in the GW approximation for the electron self energy. Furthermore, taking into account electron-hole interaction, the optical spectra of SiC-NTs are calculated by solving the Bethe-Salpeter equation (BSE) for the electron-hole amplitudes. Our GW+BSE calculations reveal the presence of excitons with a large binding energy as well as strong anisotropy in the optical properties in the low-dimensional SiC systems. The characteristics of the strongly bound electron-hole pairs or excitons in SiC nanostructures are also discussed in terms of the corresponding excitonic wavefunctions.[[notice]]補正完畢[[booktype]]紙本[[booktype]]電子