Two-dimensional (2D) MoS₂, which has great potential for optoelectronic and other applications, is thermodynamically stable and hence easily synthesized in its semiconducting 2H phase. In contrast, growth of its metastable 1T and 1T′ phases is hampered by their higher formation energy. Here we use theoretical calculations to design a potassium (K)-assisted chemical vapour deposition method for the phase-selective growth of 1T′ MoS₂ monolayers and 1T′/2H heterophase bilayers. This is realized by tuning the concentration of K in the growth products to invert the stability of the 1T′ and 2H phases. The synthesis of 1T′ MoS₂ monolayers with high phase purity allows us to characterize their intrinsic optical and electrical properties, revealing a characteristic in-plane anisotropy. This phase-controlled bottom-up synthesis offers a simple and efficient way of manipulating the relevant device structures, and provides a general approach for producing other metastable-phase 2D materials with unique properties.

二维（2D）MoS ₂在光电子和其他应用中具有巨大潜力，具有热力学稳定性，因此可以在其半导体2H相中轻松合成。相反，它们较高的形成能阻碍了其亚稳1T和1T'相的生长。在这里，我们使用理论计算来设计一种钾（K）辅助化学气相沉积方法，用于1T'MoS ₂单层和1T'/ 2H异相双层的相选择性生长。这是通过调节生长产物中K的浓度来反转1T'和2H相的稳定性来实现的。1T'MoS ₂的合成具有高相纯度的单分子层使我们能够表征其固有的光学和电学性质，从而揭示出特征性的面内各向异性。这种由相位控制的自下而上的合成方法提供了一种简单有效的方法来操纵相关的器件结构，并为生产其他具有独特特性的亚稳态2D材料提供了一种通用方法。