IMRAM

Institute of Multidisciplinary Research for Advanced Materials, Tohoku University

東北大学
多元物質科学研究所

LAST UPDATE 2021/05/06

  • 研究者氏名
    Researcher Name

    森川大輔　Daisuke MORIKAWA
    助教　Assistant Professor

  • 所属
    Professional Affiliation

    東北大学多元物質科学研究所
    Institute of Multidisciplinary Research for Advanced Materials, Tohoku University

    計測研究部門　電子回析・分光計測研究分野
    Division of Measurements, Electron-Crystallography and-Spectroscopy

  • 研究キーワード
    Research Keywords

    電子顕微鏡法
    収束電子回折法
    結晶構造解析
    Transmission electron microscopy
    Convergent-beam electron diffraction
    Crystal structure analysis
研究テーマ
Research Subject
電子回折を用いた結晶・磁気構造解析手法の開発とその応用
Crystal and magnetic structure analysis using electron diffraction

研究の背景 Background

透過型電子顕微鏡(TEM)はナノメータスケールの微小領域の解析が可能な強力な装置です．また電子回折実験では，レンズによる収差の影響がほぼないことから，従来のイメージングによる分解能を越える解析が可能です．特に収束電子回折法は，電子線の多重散乱の効果をフルに活用することで，ほとんどの空間群を一意に決定できる他，価電子分布に敏感な静電ポテンシャル分布を直接決定できることから，わずかな電子雲のズレや結合などの検出が可能であると期待されています．

Transmission electron microscopy (TEM) is a powerful tool for an analysis in nano-scale specimen areas. Electron diffraction using a TEM is not almost affected by aberrations come from lens system. Thus, it is possible to achieve higher resolution than conventional imaging techniques. Especially, convergent-beam electron diffraction (CBED) can determine almost all crystal space group uniquely using dynamical scattering effect. CBED can be also used for a determination of electrostatic potential which is sensitive for slight deviation on electron density and bonding state at valence electrons.

研究の目標 Outcome

電子顕微鏡のマイクロスコピー機能との併用により，ナノメータスケールでの精密構造解析を目指します．特に結晶界面や粒界近傍等の微小領域の解析に効果を発すると期待されます．また，機械学習を応用した2次元的な結晶情報のマッピングや，磁気構造を含めた解析にも挑戦してまいります．

By using a combination with microscopy in TEM, we develop an accurate crystal structure analysis method for nano-scale specimen area. This may be a very powerful and useful technique for analysis in interfaces of crystal and grain boundaries. We also try a 2 dimensional mapping of crystal information with using machine-learning and simultaneous analysis on magnetic structures.

研究図Research Figure

Fig.1. Electrostatic potential determined by convergent-beam electron diffraction. (a) 4 e/Å3 isosurface of FeO4 tetrahedron of room-temperature cubic phase colored with electrostatic potential and (b) that of low-temperature tetragonal phase. (c) Schematic and (d) 4 e/Å3 isosurface of hypothetical Fe 3z2−r2 orbital-ordered model. [1] Fig.2. Convergent-beam electron diffraction (CBED) patterns of SmBa2O6 at 190 K (a) [001] incidence, (b) [100] incidence. The whole pattern symmetries are (a) m and (b) 2mm, respectively. From the symmetries of CBED patterns, the space group can be determined. [2]

文献 / Publications

[1] K. Tsuda, D. Morikawa et al, Phys. Rev. B 81, 180102(R) (2010). [2] D. Morikawa et al, J. Phys. Soc. Jpn. 81, 093602 (2012).

研究者HP