二维晶体硫化物范德华异质结的界面调控及光电特性研究

Graphene and topological insulators (TIs) exhibit a variety of novel quantum effects and electromagnetic properties, which show great potential applications in low energy consumption devices, spintronics and quantum computation. At the same time, graphene and transition metal chalcogenides (TMDCs), the representative of two-dimensional (2D) atomic crystals, provide a platform for low-dimensional strong correlation systems which is extremely rich in electron, photon and phonon interaction. Isolated atomic planes can also be reassembled into unique heterostructures layer-by-layer in a precisely chosen sequence like atomic lego. Such van der Waals heterostructures have recently been fabricated and investigated, revealing unusual properties and new phenomena, exhibiting more exotic quantum manipulation and device application prospects, and is expected to bring a revolutionary breakthrough for the future information and energy technology. However, at present most of the experimental study for samples, are using the mechanical exfoliation method, which is difficult to realize the controllable preparation and precise positioning of heterostructure. The intrinsic physical properties of 2D materials is often closely associated with impurities, defects and interfaces, it is difficult to carry out a systematic study of interface engineering and optoelectronic characteristics, and to prepare controllable functional heterostructures and optoelectronic devices. This proposal aims to controllably prepare high quality 2D chalcogenides based van der Waals heterostructures with atomically sharp interface by molecular beam epitaxy (MBE) method, carry out research on the nucleation, growth kinetics and interface engineering, explore band topological properties and photoelectronic interaction mechanism of this emerging research area. With steady improvement in fabrication techniques and using graphene’s springboard, van der Waals heterostructures should develop into a large field of their own important significance for the exploration of the electronic structure of low dimensional systems and novel optoelectronic device applications.

石墨烯和拓扑绝缘体具有很多新颖的量子效应和电磁特性，在未来低能耗器件、自旋电子学和量子计算等领域具有广阔的研究和应用前景。以石墨烯、TMDC为代表的二维晶体由于电子强关联提供了极其丰富的低维体系电子、光子、声子相互作用的平台，将不同的二维材料按照某种顺序一层一层的堆栈起来形成独特的范德华异质结构，表现出更为新奇的量子调控和器件应用前景，有望为将来信息技术和能源领域带来革命性的突破。然而目前大部分用于实验研究的样品，都是利用微机械剥离的方法逐层叠加，难以实现功能异质结构的可控制备和精确定位。二维材料物性往往与杂质、缺陷和界面等密切相关，人们还未能对其界面和电子结构做系统的调控。本项目针对二维材料制备和特性研究中的关键科学问题，开展二维晶体硫化物的分子束外延生长、范德华异质结的界面、能带拓扑性质调控以及光电相互作用机理分析等研究，对于探索低维体系电子结构和性质及新型光电器件应用具有重要的意义。

过渡金属硫族化合物（TMDCs）具有很多新颖的量子效应和电磁特性，在未来低能耗器件、自旋电子学和量子计算等领域具有广阔的研究和应用前景。这类二维材料提供了极其丰富的低维体系电子、光子、声子相互作用的平台，通过组装范德瓦尔斯异质结器件有望为未来的信息技术带来革命性的突破。本项目针对TMDCs薄膜及其异质结可控制备和界面/相变调控特性研究中的关键科学问题，系统地开展了TMDCs外延生长、异质结界面耦合、原子结构和电子性质表征分析、相变物性调控以及光电相互作用机理分析等研究。在本项目支持下，研究团队取得的创新成果主要包括：（1）通过分子束外延方法可控生长出2H相和1T'相MoTe2，系统地研究了MoTe2面内异相同质结的原子结构和电子性质，为第二类外尔费米子和相变可调电子器件研究提供了条件，在国际上首次通过生长和精确退火可控制备新型半金属Mo6Te6纳米线，提出了一种结构/物相可控合成一维过渡金属硫化物纳米线的全新方法，对于构建未来新型一维/二维异质结器件和纳米器件互联集成具有重要意义；（2）通过近常压和逆向气流化学气相沉积方法可控合成出大尺寸单层、双层和少层MoSe2单晶，系统地表征分析了不同长宽比的MoSe2纳米带和MoSe2-MoS2垂直/平面异质结，证明气流速度/方向、生长/退火温度和通量比在TMDCs异质结构合成中起关键作用；（3）通过表面诱导掺杂调控制备出基于TMDCs的高增益逻辑反相器和PN结光电探测器件，实现了MoTe2薄膜的可控逐层氧化，氧化后晶体管显示由空穴载流子主导的输运特性，研究了激光功率和辐照时间对2H-到1T'-MoTe2相变的影响，揭示了相变不可逆的机制来源于Te空位的形成。在本项目资助下，研究团队共发表学术论文14篇（SCI收录12篇），参加学术会议报告12次，组织举办学术研讨会议4次，申请发明专利3项，培养研究生6名。研究成果为实现高质量TMDCs的可控制备、界面/相变调控、光电输运特性机理研究和范德瓦尔斯异质结器件应用奠定了基础。