Frontier Research Institute for Interdisciplinary Sciences
Tohoku University

For developing nanoscale functional materials and devices toward energy saving, space saving and high efficiency, it is crucial to investigate correlations between their nanoscale local structures and physical properties. For this purpose, we have been developing methods of local crystal structure and electrostatic potential analysis using convergent-beam electron diffraction (CBED).

The CBED method enables us to obtain accurate diffraction intensity data directly from specimen areas of a few nanometers in diameter. We developed an Omega-type energy-filter transmission electron microscope which can take energy-filtered CBED patterns up to a high scattering angle, and a structure analysis software package. The crystal structural parameters and electrostatic potential of a local specimen area can be determined by quantitatively fitting the experimental intensities of energy-filtered CBED patterns with multiple scattering calculations. We have also developed a new method to map local structural variations in a nanoscale spatial resolution with the combined use of the scanning transmission electron microscopy (STEM) and the CBED.

We have been applying the methods to ferroelectrics with structural phase transformations, strongly-correlated electron oxides, solid oxide fuel cell (SOFC) materials, long-period stacking order alloys, etc. We are exploring the field of nanoscale local structure analysis for more interdisciplinary applications.