低维过渡金属硫化物半导体异质结的控制生长研究

Two-dimensional transition metal dichalcogenides (2D TMDCs) electronics materials such as MoS2, which has exhibited some unique electrical and mechanical properties, which provides the possibility to realize the electronic device of next generation. As well as known, the confinement of carriers in 2D TMDCs affords excellent gate electrostatics and can potentially mitigate short channel effects, thus making them promising semiconducting channel materials for post-silicon field-effect transistors. So, dimension engineering of nanomaterials for precise control their morphology and size is the one of key techniques in developing the novel devices. ..In this project, we propose a bottom-up growth approach based on the surface induced assembly of binary atomic constituents delivers precise control over the edge termination and dimensions of TMDCs nanostructures with molecular beam epitaxy (MBE) in ultra-high vacuum (UHV). The nucleation, the growth kinetics and electrical transport properties as well as quantum effect of this kind of quasi one dimensional (1D) TMDCs electronics materials could be studied through combined surface analysis techniques. Scanning tunneling microscopy (STM) will be employed to elucidate the edge structures of 1D MoS2 etc. TMDCs nanoribbons (nanowires) at the atomic scale. Next, the edge states, spin-polarized states and charge transferring as well as optical properties in 1D TMDCs nanowires will be investigated by using surface enhancement Raman spectroscopy and scanning tunneling spectroscopy (STS). Finally, we seek to devise strategies for realization of 1D heterojunctions through the bottom-up co-synthesized 1D TMDCs nanowires. Our investigation of 1D TMDCs systems will stimulate lots of experimental and theoretical work, and accelerate the application of TMDCs in next generation nano-opto devices.

研究低维材料生长机制并调控其几何尺寸和表面形貌，是研发下一代新型功能器件的核心问题之一。随着材料尺寸进入亚纳米级别，其量子力学效应显著增强，呈现许多在量子学框架下的奇特性能。原子排列和表面结构的变化是影响纳米材料的量子力学行为最为关键的因素。本项目拟利用高真空分子束外延技术，提出利用表面模板诱导成核对低维过渡金属硫化物材料(TMDCs)的结构生长进行精确调控的构建思路，制备尺寸可精确控制的TMDCs纳米线和在此基础上的异质结等微纳结构。通过一系列表面表征技术手段深入探讨纳米线的原子结构、电子结构、边缘态、衬底间电荷转移等对其电学特性的影响；构建针对TMDCs异质结设计的微纳开关原型器件以及开展电子输运特性的理论和实验研究。此项研究有助于在亚纳米尺度下深刻理解低维材料的成核及生长的基本问题，为设计、构建下一代微纳平面电子器件提供理论指导，为开发基于TMDCs材料的新兴平面量子器件奠定基础。

本研究借助超高真空分子束外延和化学气相沉积技术生长低维过渡金属硫化物异质结和异构结，结合光电子能谱、扫描隧道显微镜、透射电镜等表征技术和输运结果对相应的微观原子结构、电子结构和宏观电性能进行研究，理解界面物理性质和材料电性能之间的关系。在项目执行期间，共发表研究论文12篇，技术专利5篇。包括1篇ACS Nano，1篇Nano Letter，1篇JPCL，1篇Adv. Mater.。受邀在国内会议和研讨会上作报告8次。培养博士生2名、硕士生2名。研究结果表明：(1)降低维度会导致新颖的拓扑性质。(2)过渡金属硫化物中的缺陷对材料的性能有重要的影响。缺陷可以诱发结构相变，是制备异质结的一种途径。(3)通过结构相变诱导同质异构结的制备，这大大提高了样品的尺寸和制备效率。(4)异质界面的性质对过渡金属硫化物的电子结构有重要的调制作用。(5) 表面分子器件构筑以及半导体材料微纳尺度发光学行为等方面研究。这些结果充分说明(1)异质界面具有新颖的物性，有利于构造新型电子器件和量子器件;(2)可以通过多种技术制备异质界面，大大提高器件制备的成功率。