Phase-contrast scanning transmission electron microscopy.
This report introduces the first results obtained using phase-contrast scanning transmission electron microscopy (P-STEM). A carbon-film phase plate (PP) with a small center hole is placed in the condenser aperture plane so that a phase shift is introduced in the incident electron waves except those passing through the center hole. A cosine-type phase-contrast transfer function emerges when the phase-shifted scattered waves interfere with the non-phase-shifted unscattered waves, which passed through the center hole before incidence onto the specimen. The phase contrast resulting in P-STEM is optically identical to that in phase-contrast transmission electron microscopy that is used to provide high contrast for weak phase objects. Therefore, the use of PPs can enhance the phase contrast of the STEM images of specimens in principle. The phase shift resulting from the PP, whose thickness corresponds to a phase shift of π, has been confirmed using interference fringes displayed in the Ronchigram of a silicon single crystal specimen. The interference fringes were found to abruptly shift at the edge of the PP hole by π.
Department of Applied Physics, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan hminoda@cc.tuat.ac.jp.
Hiroki
H
Minoda
Department of Applied Physics, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan.
Takayuki
T
Tamai
JEOL Ltd, 3-1-2 Musashino, Akishima, Tokyo 196-8558, Japan.
Hirofumi
H
Iijima
JEOL Ltd, 3-1-2 Musashino, Akishima, Tokyo 196-8558, Japan.
Fumio
F
Hosokawa
JEOL Ltd, 3-1-2 Musashino, Akishima, Tokyo 196-8558, Japan.
Yukihito
Y
Kondo
Ronchigram; STEM; contrast transfer function; phase contrast; phase plate; the principles of reciprocity