12/18 Seminar Speech

 

SpeakerProf. Naoya Shibata

OrganizationInstitute of Engineering Innovation, The University of Tokyo

TopicDirect electromagnetic field imaging of materials by atomic-resolution scanning transmission electron microscopy

Date10:20 , 2017.12.18

LocationRoom 101, Liberal Education Classroom Building

Education

Ph.D. in Engineering (Materials Science), The University of Tokyo, 2003

Experience

Professor, Institute of Engineering Innovation, The University of Tokyo, 2017-present
Associate Professor, Institute of Engineering Innovation, The University of Tokyo, 2011-2017
Assistant Professor, Institute of Engineering Innovation, The University of Tokyo, 2007-2011
Research Associate, Institute of Engineering Innovation, The University of Tokyo, 2004-2007
JSPS Research Fellow Abroad, Visiting Scientist, Oak Ridge National Laboratory, 2003-2004

Research Interests:

Prof. Naoya Shibata's research focuses on the development of new imaging techniques in scanning transmission electron microscopy and their application to grain boundaries and interfaces in oxide materials.

Abstract

Scanning transmission electron microscopy (STEM) boosted by aberration-correction technology has made possible the direct imaging and characterization of atomic and electronic structures at localized volumes of many materials and devices especially at interface regions where very interesting properties emerges. In STEM imaging, a very finely focused electron probe is scanned across the specimen and the transmitted and/or scattered electrons at each raster position are detected by the post-specimen detector(s) to form images. STEM image contrast is known to be strongly dependent on the detector geometries, and in turn we gain flexibility in determining the contrast characteristics of the STEM images by controlling the detector geometry. By elaborating special detector geometries, we can now not only image atomic structures of materials, but also can image local electromagnetic fields inside materials through differential phase contrast (DPC) imaging techniques [1]. We have been continuously developing area detectors that are capable of atomic-resolution STEM imaging. These area detectors can obtain 16 simultaneous atomic-resolution STEM images which are sensitive to the spatial distribution of scattered electrons on the detector plane [2]. By applying these area detectors, atomic-resolution DPC STEM imaging has been realized [3,4]. Having applied DPC STEM to the characterization of materials and devices, the local electric and magnetic field maps inside materials can be simultaneously obtained with ADF STEM images. We found that DPC STEM imaging is very powerful to directly characterize many interesting internal electromagnetic structures such as pn junctions in semiconductor devices [5], polar oxide interfaces and magnetic Skyrmions [6] which cannot be observed by normal STEM imaging techniques using annular type detectors.

[1] N. Shibata et al., Acc. Chem. Res., 50, 1502-1512 (2017).
[2] N. Shibata et al., J. Electro. Micros., 59, 473-479 (2010).
[3] N. Shibata et al., Nature Phys., 8, 611-615 (2012).
[4] N. Shibata et al., Nature Comm. 8, 15631 (2017).
[5] N. Shibata et al., Sci. Rep., 5, 10040 (2015).
[6] T. Matsumoto et al., Sci. Adv. 2, e1501280 (2016).