2023-05-23 アルゴンヌ国立研究所(ANL)
◆これにより、ナノ粒子の振る舞いに影響を与える格子欠陥や異質性を効果的にイメージングできるようになりました。また、この手法はAPS-U（先端光源加速器シンクロトロン施設）でのin-situ MR-BCDI（原位でのマルチリフレクション・ブラッグ干渉法）の研究を可能にしました。
◆研究では、SiCナノ粒子内部の格子変位ベクトル場を可視化することに成功しました。この成果は、ナノテクノロジー分野における新たな理解と応用の可能性を広げる重要な一歩となります。
＜関連情報＞
- https://www.anl.gov/msd/article/imaging-lattice-displacement-within-a-nanocrystal-from-multiple-coherent-bragg-peak-reflections
- https://www.nature.com/articles/s41524-023-01022-7
大域的最適化による3次元ナノ結晶格子変位の同時マルチピークブラッグコヒーレントX線回折イメージング Concurrent multi-peak Bragg coherent x-ray diffraction imaging of 3D nanocrystal lattice displacement via global optimization
Siddharth Maddali,Travis D. Frazer,Nazar Delegan,Katherine J. Harmon,Sean E. Sullivan,Marc Allain,Wonsuk Cha,Alan Dibos,Ishwor Poudyal,Saugat Kandel,Youssef S. G. Nashed,F. Joseph Heremans,Hoydoo You,Yue Cao & Stephan O. Hruszkewycz
npj Computational Materials Published:23 May 2023
DOI:https://doi.org/10.1038/s41524-023-01022-7
Abstract
In this paper we demonstrated a method to reconstruct vector-valued lattice distortion fields within nanoscale crystals by optimization of a forward model of multi-reflection Bragg coherent diffraction imaging (MR-BCDI) data. The method flexibly accounts for geometric factors that arise when making BCDI measurements, is amenable to efficient inversion with modern optimization toolkits, and allows for globally constraining a single image reconstruction to multiple Bragg peak measurements. This is enabled by a forward model that emulates the multiple Bragg peaks of a MR-BCDI experiment from a single estimate of the 3D crystal sample. We present this forward model, we implement it within the stochastic gradient descent optimization framework, and we demonstrate it with simulated and experimental data of nanocrystals with inhomogeneous internal lattice displacement. We find that utilizing a global optimization approach to MR-BCDI affords a reliable path to convergence of data which is otherwise challenging to reconstruct.
