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Xing J.,CAS Shanghai Institute of Ceramics | Xing J.,Japan National Institute of Materials Science | Takeguchi M.,Japan National Institute of Materials Science | Hashimoto A.,Japan National Institute of Materials Science | And 3 more authors.
Applied Physics Letters | Year: 2014

Photovoltaic behavior of a CaFe2O4/ZnFe 2O4 p-n multi-junction was investigated with electron holography combined with an in situ light irradiation system. Potential profiles of the samples with and without light irradiation were extracted to measure the open circuit photovoltage generated either by the whole heterojunction superstructure or from each p-n junction. Investigation on the variation in the energy band configuration under light irradiation revealed the mechanism involved in the photoelectric effect, with respect to the properties of the heterojunction and its periodic quantum structure. © 2014 AIP Publishing LLC. Source


Li W.,Nagoya University | Li W.,Global Research Center for Environment and Energy Based on Nanomaterials Science | Tanji T.,Global Research Center for Environment and Energy Based on Nanomaterials Science | Tanji T.,EcoTopia Science Institute
Microscopy | Year: 2014

Off-axis electron holography can be used to measure the inner potential of a specimen from its reconstructed phase image and is thus a powerful technique for materials scientists. However, abrupt reversals of contrast from white to black may sometimes occur in a digitally reconstructed phase image, which results in inaccurate information. Such phase distortion is mainly due to the digital reconstruction process and weak electron wave amplitude in some areas of the specimen. Therefore, digital image processing can be applied to the reconstruction and restoration of phase images. In this paper, fringe reconnection processing is applied to phase image restoration of a crystal structure image. The disconnection and wrong connection of interference fringes in the hologram that directly cause a 2π phase jump imperfection are correctly reconnected. Experimental results show that the phase distortion is significantly reduced after the processing. The quality of the reconstructed phase imagewas improved by the removal of imperfections in the final phase. © The Author 2014. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. Source


Ishida T.,Nagoya University | Ishida T.,Global Research Center for Environment and Energy Based on Nanomaterials Science | Kawasaki T.,Global Research Center for Environment and Energy Based on Nanomaterials Science | Kawasaki T.,EcoTopia Science Institute | And 7 more authors.
Microscopy | Year: 2015

A novel technique for reconstructing the phase shifts of electron waves was applied to Cs-corrected scanning transmission electron microscopy (STEM). To realize this method, a new STEM system equipped with an annular aperture, annularly arrayed detectors and an arrayed image processor has been developed and evaluated in experiments. We show a reconstructed phase image of graphite particles and demonstrate that this new method works effectively for high-resolution phase imaging. © The Author 2014. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. Source


Li W.,Nagoya University | Li W.,EcoTopia Science Institute | Zhang J.,EcoTopia Science Institute | Zhang J.,Global Research Center for Environment and Energy Based on Nanomaterials Science | And 2 more authors.
Journal of Electron Microscopy | Year: 2013

In electron holography, an abrupt reversal of contrast from white to black may occur in a digitally reconstructed phase image, potentially resulting in inaccurate phase information. There are two types of such abrupt reversals. One is a phase jump of 2π during the digital reconstruction process; in this case, the phase can be unwrapped and smoothly connected for such a jump. The other is caused by the disconnection of interference fringes due to weak electron-wave amplitude in some areas of the specimen. We propose a searching technique for finding the disconnection points based on mathematical morphology and then correcting the interference fringes. Finally, a comparatively accurate phase information image is reconstructed from the corrected interference fringes. © 2013 The Author. Source


Bui K.M.,Global Research Center for Environment and Energy Based on Nanomaterials Science | Bui K.M.,University of Tsukuba | Dinh V.A.,Osaka University | Okada S.,University of Tsukuba | And 3 more authors.
Physical Chemistry Chemical Physics | Year: 2015

The crystal and electronic structures, electrochemical properties and diffusion mechanism of NASICON-type Na3V2(PO4)3 have been investigated based on the hybrid density functional Heyd-Scuseria-Ernzerhof (HSE06). A polaron-Na vacancy complex model for revealing the diffusion mechanism is proposed for the first time in the field of Na-ion batteries. The bound polaron is found to favorably form at the first nearest V site to the Na vacancy. Consequently, the movement of the Na vacancy will be accompanied by the polaron. Three preferable diffusion pathways are revealed; these are two intra-layer diffusion pathways and one inter-layer pathway. The activation barriers for the intra-layer and inter-layer pathways are 353 meV and 513 meV, respectively. For further comparison, the generalized gradient approximation with an onsite Coulomb Hubbard U (GGA+U) is also employed. © the Owner Societies. Source

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