Man Ping, Srolovitz David, Zhao Jiong, Ly Thuc Hue
Department of Chemistry and Center of Super-Diamond & Advanced Films (COSDAF), City University of Hong Kong, Kowloon 100071, Hong Kong, China.
Department of Mechanical Engineering, The University of Hong Kong, Hong Kong 100071, Hong Kong, China.
Acc Chem Res. 2021 Nov 16;54(22):4191-4202. doi: 10.1021/acs.accounts.1c00519. Epub 2021 Oct 31.
ConspectusTwo-dimensional (2D) transition-metal dichalcogenides (TMDs) are a class of promising low-dimensional materials with a variety of emergent properties which are attractive for next-generation electronic and optical devices; such properties include tunable band gaps, high electron mobilities, high exciton binding energies, excellent thermal stability and flexibility. During the synthesis process of these materials, especially chemical vapor deposition, defects such as grain boundaries (GBs) inevitably exist. GBs are the interfaces between differently oriented grains and are line defects in 2D crystals. While GBs can degrade the overall quality of 2D materials and adversely affect some of their electrical and mechanical properties, recent results show that GBs give rise to or enhance a wide range of unique electrical, mechanical, and chemical properties of the GBs in 2D TMDs. The effects of GBs on 2D material properties are complex and diverse, providing exciting opportunities to realize new functionalities by manipulating the local structure and properties. Notably, these effects are strongly related to atom types, dislocation cores, crystal misorientation at GBs, and both in- and out-of-plane deformation. The exploitation of GBs for novel applications requires a deepened understanding of synthesis, postprocessing, defect structures, GB properties, and GB structure-property relationships in 2D materials.In this Account, we first introduce a detailed classification of GBs in 2D TMDs based on atomic structure, symmetry, and the local coordination of both transition metals and chalcogenide atoms. The GB types in typical MoS (high-symmetry hexagonal structure) and ReS (low-symmetry monoclinic structure) are taken as examples. Next, we describe the properties of GBs in 2D TMDs, including thermodynamic and kinetic, mechanical, thermal, electrical, magnetic, chemical, and electrocatalysis properties as well as several application areas where these may be exploited. Here we provide systematic atomic-level and electronic level explanations of these properties to clarify their dependences on GB structures. Applications that extend from these properties, including functional electronics, chemical sensors, and electrocatalysts, are also described. Finally, we provide several perspectives and suggest promising opportunities for exploiting the novel properties of GBs in 2D TMDs. We expect that this Account will further stimulate the fundamental research of GBs and boost the wide application of multifunctional devices.
综述二维（2D）过渡金属二硫属化物（TMD）是一类很有前景的低维材料，具有多种新兴特性，对下一代电子和光学器件具有吸引力；这些特性包括可调节的带隙、高电子迁移率、高激子结合能、出色的热稳定性和柔韧性。在这些材料的合成过程中，尤其是化学气相沉积过程中，不可避免地会存在诸如晶界（GB）之类的缺陷。晶界是不同取向晶粒之间的界面，是二维晶体中的线缺陷。虽然晶界会降低二维材料的整体质量，并对其某些电学和力学性能产生不利影响，但最近的研究结果表明，晶界会产生或增强二维TMD中晶界的一系列独特的电学、力学和化学性能。晶界对二维材料性能的影响复杂多样，为通过操纵局部结构和性能来实现新功能提供了令人兴奋的机会。值得注意的是，这些影响与原子类型、位错核心、晶界处的晶体取向差以及面内和面外变形都密切相关。要将晶界用于新应用，需要更深入地了解二维材料中的合成、后处理、缺陷结构、晶界性能以及晶界结构与性能的关系。在本综述中，我们首先基于原子结构、对称性以及过渡金属和硫属化物原子的局部配位情况，对二维TMD中的晶界进行详细分类。以典型的MoS₂（高对称性六方结构）和ReS₂（低对称性单斜结构）中的晶界类型为例。接下来，我们描述二维TMD中晶界的性质，包括热力学和动力学性质、力学性质、热性质、电学性质、磁性质、化学性质和电催化性质，以及这些性质可能被利用的几个应用领域。在此，我们对这些性质进行系统的原子级和电子级解释，以阐明它们对晶界结构的依赖性。还描述了从这些性质衍生出的应用，包括功能电子学、化学传感器和电催化剂。最后，我们提供了几个观点，并提出了利用二维TMD中晶界新特性的有前景的机会。我们期望本综述将进一步激发对晶界的基础研究，并推动多功能器件的广泛应用。
