Tungsten disulfide monolayers have attracted extensive attention in nanoelectronics and optoelectronics applications due to their remarkable electronic and optical properties. High-quality WS₂ monolayers with a scalable size and uniform thickness can be synthesized by a chemical vapor deposition method (CVD). However, they commonly contain intrinsic structural defects and different populations of charge carriers, which are responsible for different contributions of excitons, trions, and biexcitons to their photoluminescence (PL) emission. Here, we adopt sodium sulphide (Na₂S) solution to chemically treat CVD-grown WS₂ monolayers by a simple immersing method. The results show that WS₂ monolayers have a significantly enhanced PL emission by a factor of 25-fold and an obvious red-shift of the PL wavelength, resulting from the different excitonic states induced by effective n-type doping after Na₂S treatment. This work provides a simple but promising chemical doping route to significantly improve the optical properties of WS₂ monolayers and paves the way for the realization of practical WS₂ monolayer based optoelectronic applications.

中文翻译：

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通过Na ₂ S处理 ，WS ₂单层中的光致发光显着增强†

二硫化钨单层膜由于其卓越的电子和光学特性而在纳米电子学和光电子学应用中引起了广泛的关注。可以通过化学气相沉积法（CVD）合成具有可缩放尺寸和均匀厚度的高质量WS ₂单层。但是，它们通常包含固有的结构缺陷和不同的电荷载流子，这些电荷载流子负责激子，三重子和双激子对光致发光（PL）发射的不同贡献。在这里，我们采用硫化钠（Na ₂ S）溶液通过简单的浸没方法化学处理CVD生长的WS ₂单层。结果表明，WS ₂单层具有显着增强的PL发射，其发光强度提高了25倍，并且PL波长发生了明显的红移，这归因于在Na ₂ S处理后有效n型掺杂诱导的不同激子态。这项工作提供了一种简单但有希望的化学掺杂途径，以显着改善WS ₂单层的光学性能，并为实现基于WS ₂单层的实际光电应用铺平了道路。