2019 Fiscal Year Final Research Report

Ultrahigh time and space resolved spectroscopy and its application to the study of photo-iduced phase transition

Research Project

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Project/Area Number	16K13822
Research Category	Grant-in-Aid for Challenging Exploratory Research
Allocation Type	Multi-year Fund
Research Field	Condensed matter physics I
Research Institution	Osaka City University (2019) Osaka University (2016-2018)
Principal Investigator	Kanasaki Jun'ichi 大阪市立大学, 大学院工学研究科, 教授 (80204535)
Co-Investigator(Kenkyū-buntansha)	木曽田賢治和歌山大学, 教育学部, 教授 (90243188)
Project Period (FY)	2016-04-01 – 2020-03-31
Keywords	分光 / 光誘起相転移 / 新構造相創成 / ナノ構造 / グラファイト / グラフェン
Outline of Final Research Achievements	By using scanning tunneling microscopy, we have reviealed the primary steps included in the excitation-induced phase transformation, such as nucleation and proliferation of sp3-like interlayer bonds. The growth mode of photo-induced structures strongly depends on the photon energy, and these results are interpreted by different dynamical pathways for the nucleation and proliferation of interlayer-bonded phase. The findings of our investigation can provide a key to the optical control of sp2-to-sp3 conversion and the organization with the nano-scaled products in graphene-related materials. Also, we studied the structural stability of graphene on SiC under pulsed laser iraadiations. We analyzed the evolution of 2D Raman peak of graphene layers, and revealed that optical excitation removes graphene layer selectively from multiple graphene-layer region, forming single atomic-layer graphene on SiC which is stable against the excitation.
Free Research Field	固体物性
Academic Significance and Societal Importance of the Research Achievements	グラファイトにおける光誘起構造相転移の過程で生成される核構造や新規構造相の成長過程の原子論的解明に成功すると共に、核形成と新構造相の成長過程が示す異なる波長依存性を明確にした。物性物理学的に重要な知見を得ると共に、光による構造制御に向けた可能性を拓いた。また、光励起に対するグラフェン構造の安定性が原子層数に強く依存することを発見し、光励起による単層グラフェンの精製技術の可能性を示した。グラフェンの特異な電子的特性や機械特性はグラフェンの原子層数に強く依存しており、本研究の成果は応用物理学及び材料科学分野において大きな波及効果が期待でき、社会的意義は大きいものと評価できる。