High contrast STEM imaging for light elements by an annular segmented detector

Kousuke Ooe; Takehito Seki; Yuichi Ikuhara; Naoya Shibata

doi:10.1016/j.ultramic.2019.04.011

High contrast STEM imaging for light elements by an annular segmented detector

Ultramicroscopy. 2019 Jul:202:148-155. doi: 10.1016/j.ultramic.2019.04.011. Epub 2019 Apr 23.

Authors

Kousuke Ooe¹, Takehito Seki¹, Yuichi Ikuhara², Naoya Shibata³

Affiliations

¹ Institute of Engineering Innovation, School of Engineering, the University of Tokyo, Yayoi 2-11-16, Bunkyo, Tokyo 113-0032, Japan.
² Institute of Engineering Innovation, School of Engineering, the University of Tokyo, Yayoi 2-11-16, Bunkyo, Tokyo 113-0032, Japan; Nanostructure Research Laboratory, Japan Fine Ceramics Center, Mutsuno 2-4-1, Atsuta, Nagoya 456-8587, Japan.
³ Institute of Engineering Innovation, School of Engineering, the University of Tokyo, Yayoi 2-11-16, Bunkyo, Tokyo 113-0032, Japan; Nanostructure Research Laboratory, Japan Fine Ceramics Center, Mutsuno 2-4-1, Atsuta, Nagoya 456-8587, Japan. Electronic address: shibata@sigma.t.u-tokyo.ac.jp.

PMID: 31054384
DOI: 10.1016/j.ultramic.2019.04.011

Abstract

Annular bright-field scanning transmission electron microscopy (ABF STEM) has been actively used to directly observe the light element atoms inside materials and devices. However, the detector angle condition for conventional ABF STEM has been empirically selected and thus is not always optimized for observing ultra-light element atoms such as hydrogen and lithium atoms. In this study, the detector conditions for ABF STEM were reexamined by calculating a new type of phase contrast transfer function (PCTF) for an annularly segmented detector to maximize the image contrast of ultra-light element atoms such as lithium. Using this new PCTF, an improved detector geometry for observing lithium atoms is demonstrated, which is confirmed by the image simulations and experiments in several types of lithium cathode materials.

Keywords: Annular bright-field; Lithium-rich cathode; Phase contrast; Scanning transmission electron microscopy (STEM); Segmented detector.