Atomic-Scale Analysis and Dynamic Observation of 2D Layered Materials
Prof. Zhong-Chang Wang
International Iberian Nanotechnology Laboratory (INL)

III-VI semiconductors are currently being investigated as potential candidates for many applications. Among several III-VI semiconductors, In-Se systems are an interesting type of materials due to their multiple phases and excellent optical properties. There are at least five different phases of In2Se3(α, β, γ, δ, and κ). The α and β -phases can crystallize in both α(3R) and α(2H) crystal structures while γ -phase has a defective wurtzite structure. The κ–phase is reported to have a structure more similar to the α-phase with larger unit cell. On the other hand, InSe also has several different phases, which hold substantial potential device applications.
Here, we investigate how the growth temperature, fluxes and type of substrates (GaAs (100), GaAs (111) A and Mica) influence the growth of In2Se3 and find the optimum parameters for obtaining phase controlled In2Se3. We found that Se-rich and high temperatures favour growth of β phase In2Se3 while γ phase is obtained in In-rich conditions and low temperatures on GaAs (100) substrates. Within the same parameter range, γ phase was predominant on GaAs (111) A substrates. On the other hand, we also report the formation of stable free-standing 1D atomic chains derived from 2D InSe and GaSe layered materials by directly thermal treatment at elevated temperature. We demonstrate that mono-selenide layered material experiences a transformation from 2D edge of zigzag structure to 1D atom chain by in situ aberration-corrected transmission electron microscopy (AC-TEM). The TEM snapshots reveal the atomic-scale formation mechanism of free-standing 1D chains and reconstruction process of (001) edge. The electronic structure and quantum electron transport of such chain structures were also studied by first-principles calculations, which is associated with functional properties for quantum devices.

About the Speaker

王中长, 欧洲国际伊比利亚纳米技术实验室高级研究员、教授、课题组长。2008获东京大学博士学位, 2008至2017年, 任日本东北大学助手、助理教授, 副教授。2016年, 英国伦敦大学学院访问教授。2017年, 任欧洲国际伊比利亚纳米技术实验室课题组长。从事新型低维、纳米及能源材料的原子层面制备、表征、性能及第一性原理和分子动力学计算, 在新材料及功能缺陷的基础原子电子结构与其物理化学性能直接关联方面进行了深入研究, 开发新型超薄功能器件。负责20多项包括国家自然科学基金委、欧洲研究经费、日本国文部省科学研究费等项目。在国际著名学术期刊Nature, Nature Nanotech., Nature Commun.等杂志上发表SCI检索论文300余篇, 参与两部英文专著撰写; 在50多个主要的国际会议上做邀请或专题报告。获日本材料学会材料研究促进奖, 国际材料联合会年轻科学家奖, NEC最高科学技术奖, IAAM科学家奖章等。

2023-08-30 4:00 PM
Room: A403 Meeting Room
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