One-pot chemical vapor deposition (CVD) growth of large-area Janus SeMoS monolayers is reported, with the asymmetric top (Se) and bottom (S) chalcogen atomic planes with respect to the central transition metal (Mo) atoms. The formation of these 2D semiconductor monolayers takes place upon the thermodynamic-equilibrium-driven exchange of the bottom Se atoms of the initially grown MoSe₂ single crystals on gold foils with S atoms. The growth process is characterized by complementary experimental techniques including Raman and X-ray photoelectron spectroscopy, transmission electron microscopy, and the growth mechanisms are rationalized by first principle calculations. The remarkably high optical quality of the synthesized Janus monolayers is demonstrated by optical and magneto-optical measurements which reveal the strong exciton–phonon coupling and enable an exciton g-factor of −3.3.

中文翻译：

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高光学质量大面积单层 Janus 过渡金属二硫化物的化学气相沉积

报道了大面积 Janus SeMoS 单层的一锅化学气相沉积 (CVD) 生长，相对于中心过渡金属 (Mo) 原子具有不对称的顶部 (Se) 和底部 (S) 硫属元素原子平面。这些 2D 半导体单层的形成发生在最初生长的 MoSe _{2的底部 Se 原子的热力学平衡驱动交换上}带有 S 原子的金箔上的单晶。生长过程的特点是互补的实验技术，包括拉曼和 X 射线光电子能谱、透射电子显微镜，并且通过第一性原理计算使生长机制合理化。通过光学和磁光测量证明了合成的 Janus 单层的非常高的光学质量，这些测量揭示了强的激子 - 声子耦合并使激子g因子为 -3.3。