Tetsuji Kodama

Phase reconstruction in annular bright-field scanning transmission electron microscopy

A novel technique for reconstructing the phase shifts of electron waves was applied to Cs-corrected scanning transmission electron microscopy (STEM). To realize this method, a new STEM system equipped with an annular aperture, annularly arrayed detectors and an arrayed image processor has been developed and evaluated in experiments. We show a reconstructed phase image of graphite particles and demonstrate that this new method works effectively for high-resolution phase imaging.

Development of Compact Cs/Cc Corrector with Annular and Circular Electrodes

The spherical aberration (Cs) correction is indispensable to improve the spatial resolution in the electron microscopes. Some types of Cs correction devices have been proposed and developed, and the Cscorrectors consisted of multi-pole lenses have successfully realized sub-angstrom resolution in (S)TEMs [1-2]. However, these correctors require complex control of multiple optical components with high accuracy and stability. They also demand reconfiguration of the microscope columns to insert rather large additional components, resulting in huge cost. In order to solve these problems, Ikuta had proposed a very simple and compact Cs-corrector with axially-symmetric electrostatic-filed formed between annular and circular electrodes [3-4], as schematically shown in Fig. 1(a). We called it “ACE corrector” (the Cscorrector using Annular and Circular Electrodes). Furthermore, this simple device has an additional capability to reduce the effect of the chromatic aberration (Cc). In the present paper, we report the principle of Cs/Cc correction and preliminary results of the ACE corrector in simulations and experiments.

STEM Phase Imaging by Annular Pixel Array Detector (A-PAD) Combined with Quasi-Bessel Beam

Tadahiro Kawasaki, Takafumi Ishida, Tetsuji Kodama, Takayoshi Tanji and Takashi Ikuta, 1. Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya, Japan 2. Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya, Japan 3. Global Research Center for Environment & Energy based on Nanomaterials Science, Tsukuba, Japan 4. Graduate School of Science & Technology, Meijo University, Nagoya, Japan 5. Faculty of Engineering, Osaka Electro-Communication University, Neyagawa, Japan

Simple and Compact Electrostatic Cs-Corrector using Annular and Circular Electrodes

1. Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya, Japan 2. Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya, Japan 3. Graduate School of Science & Technology, Meijo University, Nagoya, Japan 4. Vacuum Device Ltd., Mito, Japan 5. Faculty of Science and Engineering, Kinki University, Higashiosaka, Japan 6. Faculty of Engineering, Osaka Electro-Communication University, Neyagawa, Japan

Two-electron interference in a coherent beam

The interference between quantum amplitude for two electrons, emitted from two source points, to be detected at two detection points, is a direct result of quantum exchange statistics. Such interference is observed in the coincidence probability, compared with that of statistically independent electrons, by computing the time correlation function from the arrival times of the electrons. When the two detectors are separated by a distance less than the coherence length, the coincidence probability is suppressed for electrons (antibunching) due to the Pauli principle, even though they do not interact with each other. However, electrons are charged particles. The Coulomb potential, which governs the scattering of one charged particle by another, is so long ranged. It is obvious that we must consider the Pauli principle and the Coulomb interactions simultaneously. This paper deals with basic experimental and theoretical investigations of the antibunching behavior of electrons in a free beam by considering the Pauli principle and the direct Coulomb interaction between two individual electrons. The experimentally found dependences are described in a model which considers the Coulomb scattering and theoretical values of correlation signals evaluated by analytical calculations agree with those determined by experiment. A study of the time correlation function from the arrival times of the electrons will lead to an understanding of the physical processes that take place in electron guns.