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Three-dimensional analysis of Eu dopant atoms in Ca-alpha-SiAlON via through-focus HAADF-STEM imaging

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Title: Three-dimensional analysis of Eu dopant atoms in Ca-alpha-SiAlON via through-focus HAADF-STEM imaging
Authors: Saito, Genki Browse this author →KAKEN DB
Yamaki, Fuuta Browse this author
Kunisada, Yuji Browse this author
Sakaguchi, Norihito Browse this author
Akiyama, Tomohiro Browse this author
Keywords: Dopant distribution
Image simulation
Aberration correction
Issue Date: Apr-2017
Publisher: Elsevier
Journal Title: Ultramicroscopy
Volume: 175
Start Page: 97
End Page: 104
Publisher DOI: 10.1016/j.ultramic.2017.01.014
Abstract: Three-dimensional (3D) distributional analysis of individual dopant atoms in materials is important to development of optical, electronic, and magnetic materials. In this study, we adopted through-focus high-angle annular dark-field (HAADF) imaging for 3D distributional analysis of Eu dopant atoms in Ca-alpha-SiAION phosphors. In this context, the effects of convergence semi-angle and Eu z-position on the HAADF image contrast were investigated. Multi-slice image simulation revealed that the contrast of the dopant site was sensitive to change of the defocus level. When the defocus level matched the depth position of a Eu atom, the contrast intensity was significantly increased. The large convergence semi angle greatly increased the depth resolution because the electron beam tends spread instead of channeling along the atomic columns. Through-focus HAADF-STEM imaging was used to analyze the Eu atom distribution surrounding 10nm cubes with defocus steps of 0.68nm each. The contrast depth profile recorded with a narrow step width clearly analyzed the possible depth positions of Eu atoms. The radial distribution function obtained for the Eu dopants was analyzed using an atomic distribution model that was based on the assumption of random distribution. The result suggested that the Ca concentration did not affect the Eu distribution. The decreased fraction of neighboring Eu atoms along z-direction might be caused by the enhanced short-range Coulomb-like repulsive forces along the z-direction. (C) 2017 Elsevier B.V. All rights reserved.
Rights: © 2017. This manuscript version is made available under theCC-BY-NC-ND 4.0 license
Type: article (author version)
Appears in Collections:エネルギー・マテリアル融合領域研究センター (Center for Advanced Research of Energy and Material) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 齊藤 元貴

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