2017 Fiscal Year Annual Research Report
| Project/Area Number |
17F17719
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| Research Institution | Kyoto University |
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Principal Investigator |
島川 祐一 京都大学, 化学研究所, 教授 (20372550)
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| Co-Investigator(Kenkyū-buntansha) |
HEO YOOUN 京都大学, 化学研究所, 外国人特別研究員
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| Project Period (FY) |
2017-07-26 – 2019-03-31
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| Keywords | ヘテロ構造 / 遷移金属酸化物 |
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| Outline of Annual Research Achievements |
本研究では、遷移金属酸化物中の酸素配位環境に着目し、ヘテロ構造化や酸化還元反応などで酸素配位環境を制御することで、酸化物の新機能開発を目指すものである。パルスレーザー堆積法で作製した酸素欠損型鉄酸化物エピタキシャル薄膜を対象として研究を展開してきた。酸化反応で薄膜中の酸素量を制御し、それに伴う構造や伝導性の変化を調べることで、薄膜中の酸素イオンダイナミクスに起因した新奇な伝導現象を見出している。これらの結果は、薄膜中の酸素イオンダイナミクスや酸素配位環境の制御が物質機能開拓に重要であることを示している。
Our goal of this research project is to develop a systematic approach to control nanoscale oxygen coordination environments in oxide heterostructures and to explore novel functional properties, which will serve as a basis for not only electronic but also electrochemical devices.
In this respect, we focus on epitaxial thin films of oxygen deficient SrFeO2.5, grown by pulsed laser deposition. We investigate oxidation-induced changes in structural and electronic conduction properties of the films and found that electronic conductions are locally enhanced, revealing preferred sites for oxygen diffusions. Furthermore, we show that the oxygen coordination environment and the conduction properties can be controlled by applying electric biases and by inducing redox reactions. These results highlight the role of nanoscale oxygen dynamics and resultant redox reactions in SrFeO2.5.
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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
ブラウンミレライト鉄酸化物SrFeO2.5のエピタキシャル薄膜に対して、薄膜中の酸素配位環境の変化を走査プローブ顕微鏡による評価を中心に行ってきた。その結果、酸化還元反応を施したSrFeO2.5薄膜は薄膜中の酸素量変化に伴って伝導度が局所的に増加することを見出した。また薄膜表面のテラスのある特定の場所でのみ伝導度の増加が見られた。一連の結果は酸化反応に伴う酸化物イオンの取り込みが局所的に起こっていることを意味している。
We paid our attentions to epitaxial thin films of brownmillerite structured SrFeO2.5 and investigated how oxygen coordination environments influence structural and electronic conduction properties of the films. Because changes in oxygen coordination environments in the films are expected to occur locally, we mainly employed scanning probe microscope (SPM). In fact, we spent some time in establishing the set-up of the SPM observations. The SPM observations revealed that by oxidizing the film (increasing the oxygen contents), the electronic conductions are locally enhanced and this enhancements are seen at specific sites on terraces of the films. This indicates that oxygen incorporations associated with the oxidation reactions preferentially occurs at the specific sites. The results provide deep insights on how oxygen coordination environments affect structural and physical properties of oxide heterostructures, and leads to further understanding of oxygen ion dynamics in them.
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| Strategy for Future Research Activity |
遷移金属酸化物中の酸素配位環境に着目した物質機能開発を継続する。より具体的には、鉄酸化物だけではなく、他の3d遷移金属（例えばCo、Mn）を含んだ酸化物から構成されるヘテロ構造中の酸素配位環境の制御を行い、構造、伝導性、磁気特性および誘電特性などの観点から機能特性の開発を行う。
Over the coming year, we continue investigating oxygen coordination environments and functional properties in transition metal oxides that include various 3d transition metals like Co and Mn rather than Fe. Controlling oxygen coordination environments in such oxides will be done by making heterostructures with structurally different materials and by applying redox reactions. We expect to see some change in physical properties such as electronic conductions, magnetic and dielectric properties in association with changes in the oxygen coordination environments. Through such attempts, we will establish an approach to control the oxygen coordination environments and will explore novel properties emerging in oxide heterostructures.
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Research Products
(3 results)
