2021 Fiscal Year Research-status Report
Accurate site-selective atomic structure determination by single-energy x-ray holography
| Project/Area Number |
20K15027
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| Research Institution | Hiroshima University |
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Principal Investigator |
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| Project Period (FY) |
2020-04-01 – 2024-03-31
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| Keywords | site-selectivity / x-ray holography / atomic structure / local atomic environment |
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| Outline of Annual Research Achievements |
The concept of site-selectivity is of great importance for modern materials science. It entails a full understanding of the atomic scale structure of the functional site in a material, which in turn largely determines its functional properties. New advances in x-ray fluorescence holography (XFH) have the potential to become a universal tool for site-selective investigations in crystals. These methods combine the intrinsic element-selectivity of XFH with the possibility for a chemical characterization of the environment. This is achieved by a resonant approach, i.e. tuning the x-ray energy to an energy that coincides with an x-ray absorption edge in the material. However, the approach is practically limited in the choice of energies, and the reconstruction from single-energy holographic data is still problematic. The proposed project aims to resolve these problems, to practically implement site-selective measurements and to apply them to current research issues in materials science.
This approach is useful for, among else, identifying local atomic environments with chemical information and for understanding in detail the chemical disorder. One of the obstacles here is the atomic image cancellation effect.
In particular, the case of a special material, i.e. Mn doped Bi2Te3, was analyzed. This material is of scientific and technological interest as a topological insulator. Previous experiments have found two possible sites for the Mn atom, in which the type of the neighboring atoms (Bi or Te) could not be identified. This can be clarified by this project.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The project is progressing smoothly.
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| Strategy for Future Research Activity |
The next step of the project is to test the application of the developed concepts to more complex systems. We will start with Ni-Fe alloys of the "invar" family, where information targeted on the specific correlations between Ni-Ni (or Fe-Fe) short-range order pairs is a highly sought after. Subsequently, even more complex structures as those in decagonal quasicrystals, can be targeted.
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| Causes of Carryover |
In FY 2021, many large international conference were still held only online due to the Pandemic situation. The budget set aside to present the research at international conferences could not therefore not be used fully. It will be used in FY2022 for the same purpose.
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