2019 Fiscal Year Final Research Report

Cross-over states in coherent thin films under self-generated stress fields and their functionality

Research Project

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Project/Area Number	17K18970
Research Category	Grant-in-Aid for Challenging Research (Exploratory)
Allocation Type	Multi-year Fund
Research Field	Materials engineering and related fields
Research Institution	Tohoku University
Principal Investigator	Toyohikjo Konno 東北大学, 金属材料研究所, 教授 (90260447)
Co-Investigator(Kenkyū-buntansha)	白石貴久東北大学, 金属材料研究所, 助教 (50758399) 木口賢紀東北大学, 金属材料研究所, 准教授 (70311660)
Project Period (FY)	2017-06-30 – 2020-03-31
Keywords	強誘電体 / 酸化物薄膜 / 透過電子顕微鏡 / エックス線回折
Outline of Final Research Achievements	Ferro-electric oxide family constitutes one of the indispensible functional material in civilized world. Examples include ultrasonic devices for sensing equipment, memory devices for IT society, and low energy harvester in energy-saving machines. It is widely known that the ferro-electric properties sensitively depends on the crystallographic structure, which in return, is a function of composition of the oxides and external stress fields. This study was initiated therefore in order to elucidate the effects of composition and applied stress fields on the stability of the ferro-electric oxide phases. Thin perovskite-type oxide films have been fabricated on substrates with various lattice constants by using a chemical solution deposition method, and the structures of these films were examined by X-ray diffraction and transmission electron microscopy. Our results demonstrated that morphologic phase boundaries depends on both the character of transition metal and applied stress.
Free Research Field	材料物性
Academic Significance and Societal Importance of the Research Achievements	酸化物強誘電体材料は、エコーなどの超音波デバイス、記憶媒体であるメモリデバイス、あるいはエナジーハーベスターといった様々な分野で利用されている材料である。強誘電体特性は構造敏感な特性であり、酸化物の組成や応力場に依存する。本研究は特異な誘電特性をもつペロブスカイト型酸化物の相安定性に対する組成と応力場の関係を解明することを目的して開始された。今回の研究により、強誘電体特性をデバイス等に薄膜形状で最大限の効率で応用する際の材料設計として、ペロブスカイト型酸化物を構成する遷移金属元素の大きさ及び基板の選択が重要な要素であることが判明した。