73rd CEMS Colloquium

Functional materials supporting our life are constructed from atomic arrangements. Thus atomic-scale observations are important to understand fundamental structures and understand how materials functions occur. Electron holography using coherency of electron wave can observe not only atomic position but also electromagnetic fields in the materials. To push the limit of electron holography, we have developed varieties of technologies and applications.

1) Split-illumination electron holography has been developed by employing multiple biprism to overcome difficulties in field of view due to lateral coherence length of the electron wave and expand application fields of electron holography [1].

2) Holographic tomography has been developed to observe three-dimensional magnetic fields in nanoscale magnetic vortices [2]. The high penetration power of a high energy electron wave is crucial to observing magnetic structures, which exist only in thick samples.

3) A 1.2-MV aberration corrected high voltage transmission electron microscope (TEM) has been developed. This is the only one TEM with aberration corrector in high acceleration voltage category. The resolution of 43 pm has been realized in electrostatic observations [3]. The microscope has also been applied to the magnetic field observations of CoFeB/Ta multilayer at 0.67 nm resolution (Fig. 1) [4].

Recently we are developing new technologies of electron holography using informatics to improve sensitivity of electron holography. I would like to discuss about the future perspective of electron holography.

[1] T. Tanigaki et al., Appl. Phys. Lett., 101 (2012) 043101.
[2] T. Tanigaki et al., Nano Lett., 15 (2015) 1309.
[3] T. Akashi et al., Appl. Phys. Lett., 106 (2015) 074101.
[4] T. Tanigaki et al., Sci. Rep., 7 (2017) 16598.

Development of the 1.2 MV holography microscope was supported by a grant from the Japan Society for the Promotion of Science (JSPS) through the “Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST Program)” initiated by the Council for Science, Technology, and Innovation (CSTI). Part of this research was supported by JST CREST Grant Number JPMJCR1664, Japan.