二维层状过渡金属硫族化合物化学气相沉积生长机理的电子显微研究

This research project will focus on resolving the microscopic growth mechanism of chemical vapor deposition growth of two-dimensional (2D) transition metal dichalcogenides (TMD). Due to the difficulties on monitoring the growth process in situ at high spatial resolution, and the problems occurring during the samples, particularly for the nuclei and early-stage products during the CVD growth of 2D materials, our current understanding on the growth mechanism of the CVD growth of 2D TMD materials is quite limited. To address this issue, we are planning to conduct “transfer-free” CVD-TEM study jointly to precisely monitor the growth products at different stages, which were grown directly on graphene-like ultrathin membranes. .With the assistance of aberration-corrected transmission electron microscopy, we shall be able to directly resolve the atomic structures and chemical components of the as-grown TMD materials at different stages. Further information will be obtained from in situ TEM study via performing the mini-CVD growth within a graphene or SiNx/SiN based micro-reaction cells inside the TEM chamber. Combining these results via careful TEM characterization and analysis, we shall be able to determine the mechanisms responsible for the mass conveyor, nucleation, edge formation with certain termination and structures, grain/phase boundaries. .Two scholars from abroad-Prof. Jun Yuan from University of York, UK, and Dr. Zheng Liu from Nanyang Technological University, SG were invited to join this project, both of whom have long-term collaborations with the PI. They will contribute to this project on the numerical modeling of CVD process, and the conventional CVD growth respectively. .Overall, during the coming 4-year project (or even longer time), we are planning to capture the key parameters and primary growth mechanism for the CVD growth of 2D TMD materials. More importantly, with the success of our joint CVD-TEM studies, we hope to propose a few practical routes for the CVD growth of 2D TMD materials with precise controls, which may pave ways for the application of 2D TMD materials.

本项目以二维过渡金属硫族化合物材料的微观生长机理为研究主题，考虑到形核初期难以成像、样品转移等困难，提出以原子分辨电子显微表征为主要手段，利用石墨烯、超薄氧化硅等电镜载网，实现CVD制备二维TMD材料与电镜观察和和表征的无缝、“无转移对接”，并结合电镜下的原位生长手段，期望揭示二维TMD材料化学气相沉积过程中形核、生长的微观过程和机理；晶畴团聚、晶界和畴界的形成和规律；尺寸、边缘结构和缺陷的调控，为精确可控合成奠定基础。项目组成员中还引入了英国约克大学Jun Yuan教授和新加坡南洋理工大学Liu Zheng博士两位海外专家，在CVD合成条件的数值模拟、常规CVD合成等方面开展合作，也为本项目的顺利实施提供了有利条件。我们希望通过四年时间的努力，在上述二维TMD材料CVD合成重要过程和微观机理的探索上取得一系列重要的原创性科研成果，推动二维TMD材料合成和器件应用等领域发展。

二维过渡金属硫族化合物材料有望作为后摩尔时代集成电路的核心沟道材料，但目前材料的高质量可控制备仍存在挑战，其中一个关键因素是深入理解生长行为和机理，进而掌握调控机制。.本项目提出利用先进电子显微表征技术，与主流化学气相沉积和分子束外延合成技术紧密结合，揭示以MoS2为代表的二维过渡金属硫族化合物材料(TMDC)的围观生长行为和机理，取得的主要研究成果有：.1、.从截面表征出发，揭示了二维材料的形核和生长行为和机理对衬底的依赖性，阐明晶圆级单晶二维TMDC材料制备的关键；.2、.利用石墨烯电镜载网，基于离位和原位生长，解析二维TMDC材料的形核和早期生长行为和机理；.3、.基于定量、统计原子分辨电镜表征，绘出二维TMDC材料中点缺陷的类型和浓度对生长条件的依赖关系，给出调控机理；.4、.阐明制备晶圆级单晶二维TMDC材料的关键机制，并通过和相关CVD、MBE合成小组合作，初步完成晶圆级单晶TMDC材料的制备。.5、.项目直接经费60万，已执行58.73万，执行率97.88%。.项目执行期内共发表SCI收录学术论文40篇，其中影响因子大于3的39篇， 影响因子大于7的23篇，包括Advanced Materials 1篇，ACS Nano 3 篇， Nano Letters 2篇，Advanced Function Materials 2篇，Nano Research 3篇，Nanoscale 2篇等，目前总引用330余次。出版英文专著章节1章。.在项目组全体成员的共同努力下，在合作小组的支持下，顺利完成！