The advent of two-dimensional transition metal dichalcogenides (2D-TMDs) has led to an extensive amount of interest amongst scientists and engineers alike and an intensive amount of research has brought about major breakthroughs in the electronic and optical properties of 2D materials. This in turn has generated considerable interest in novel device applications. With the polymorphic structural features of 2D-TMDs, this class of materials can exhibit both semiconducting and metallic (quasi-metallic) properties in their respective phases. This polymorphic property further increases the interest in 2D-TMDs both in fundamental research and for their potential utilization in novel high-performance device applications. In this review, we highlight the unique structural properties of few-layer and monolayer TMDs in the metallic 1T- and quasi-metallic 1T′-phases, and how these phases dictate their electronic and optical properties. An overview of the semiconducting-to-(quasi)-metallic phase transition of 2D-TMD systems will be covered along with a discussion on the phase transition mechanisms. The current development in the applications of (quasi)-metallic 2D-TMDs will be presented ranging from high-performance electronic and optoelectronic devices to energy storage, catalysis, piezoelectric and thermoelectric devices, and topological insulator and neuromorphic computing applications. We conclude our review by highlighting the challenges confronting the utilization of TMD-based systems and projecting the future developmental trends with an outlook of the progress needed to propel this exciting field forward.

中文翻译：

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二维过渡金属二硫属化物的最新进展：（准）金属相的相变和应用

二维过渡金属二硫属化物 (2D-TMD) 的出现引起了科学家和工程师的广泛兴趣，大量研究为二维材料的电子和光学特性带来了重大突破。这反过来又引起了对新型设备应用的极大兴趣。凭借 2D-TMD 的多晶结构特征，此类材料可以在其各自的相中同时表现出半导体和金属（准金属）特性。这种多态性进一步增加了对 2D-TMD 在基础研究和新型高性能设备应用中的潜在利用的兴趣。在这次审查中，我们强调了金属 1T 相和准金属 1T' 相中少层和单层 TMD 的独特结构特性，以及这些相如何决定它们的电子和光学特性。将涵盖 2D-TMD 系统的半导体到（准）金属相变的概述以及相变机制的讨论。将介绍（准）金属 2D-TMD 应用的当前发展，从高性能电子和光电器件到能量存储、催化、压电和热电器件，以及拓扑绝缘体和神经形态计算应用。