A research group led by Professor Shinya Hosokawa of Kumamoto University combined conventional methods and new technologies to determine the atomic positions of impurity elements that could not be obtained by ordinary diffraction experiments or electron microscopy for the first time in the world.
In many materials, the performance is often exhibited by adding a small amount of different elements, and it is important to understand the effect of the added element on the atomic structure to improve the performance.
In this study, we determined the site (position) to which Mn is added to tellurized bismuth (Bi2Te3), which contains manganese (Mn) as an impurity.This substance is one of the "topological insulators" that are attracting attention as a new energy-saving and high-speed computer material. The inside is an insulator that does not conduct electricity, but the surface is a substance with almost zero electrical resistance.
This time, in order to accurately obtain the atomic arrangement around impurities, we combined the conventional method "X-ray absorption fine structure spectroscopy (XAFS)" with the new technology "fluorescent X-ray holography (XFH) method".Furthermore, by adopting a new analysis method called "sparse modeling" instead of the conventional mathematical method (Fourier transform), the atomic image of the impurity Mn in tellurized bismuth could be reproduced extremely clearly.
By applying this technology, it is expected that the functions of semiconductor materials, magnetic materials, etc. whose performance is controlled by additive elements can be elucidated, and that new guidelines will be given to the development of new materials.
In addition, this achievement is due to joint research with Hiroshima City University, Nagoya Institute of Technology, Hiroshima Institute of Technology, University of Toyama, Yamagata University and multiple research institutes.Researchers from small and medium-sized universities, from the idea of research themes to sample preparation, experiments, and data analysis, collaborated with each other and used a general-purpose synchrotron radiation X-ray light source. It is also said to be significant in terms of social contribution.
