title: Reversible contrast in focus series of annular bright field images of a crystalline LiMn₂O₄ nanowire.
abstract: A through-focus series of annular bright field (ABF) images were observed simultaneously with high-angle annular dark field (HAADF) images of very thin lithium manganese oxide (LiMn₂O₄), a typical cathode material used in lithium ion batteries, using a spherical aberration corrected electron microscope with a 50 pm resolution (R005). The ABF images showed dark dips at the positions of Li and Mn--O atomic columns, which reversed to bright peaks when the defocus sign was changed, as commonly observed in phase contrast images. The optimal defocus for the ABF images was about 2 nm of over-focus, while that for the HAADF images was 2 nm of under-focus for an incident probe with a convergent semi-angle of 30 mrad. These experimental results are interpreted based on a weak-phase-object approximation.
authors.affiliation: Department of Condensed Matter Physics, Tokyo Institute of Technology, 2-12-1-H-51 Oh-okayama, Meguro-ku, Tokyo 152-8551, Japan.
authors.forename: Soyeon
authors.initials: S
authors.lastname: Lee
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Oshima
authors.forename: Eiji
authors.initials: E
authors.lastname: Hosono
authors.forename: Haoshen
authors.initials: H
authors.lastname: Zhou
authors.forename: Kunio
authors.initials: K
authors.lastname: Takayanagi