Monolayer transition metal dichalcogenides (TMDCs) are promising materials for next generation optoelectronic devices. The exciton diffusion length is a critical parameter that reflects the quality of exciton transport in monolayer TMDCs and limits the performance of many excitonic devices. Although diffusion lengths of a few hundred nanometers have been reported in the literature for as-exfoliated monolayers, these measurements are convoluted by neutral and charged excitons (trions) that coexist at room temperature due to natural background doping. Untangling the diffusion of neutral excitons and trions is paramount to understand the fundamental limits and potential of new optoelectronic device architectures made possible using TMDCs. In this work, we measure the diffusion lengths of neutral excitons and trions in monolayer MoS₂ by tuning the background carrier concentration using a gate voltage and utilizing both steady state and transient spectroscopy. We observe diffusion lengths of 1.5 μm and 300 nm for neutral excitons and trions, respectively, at an optical power density of 0.6 W cm^–2_.

中文翻译：

---

单层MoS2中的中性激子扩散。

单层过渡金属二硫化碳（TMDC）是下一代光电器件的有前途的材料。激子扩散长度是一个关键参数，它反映了单层TMDC中激子传输的质量，并限制了许多激子器件的性能。尽管在文献中已经报道了剥落的单层膜的扩散长度为几百纳米，但由于自然背景掺杂，这些测量结果在室温下共存于中性和带电激子（三重子）中。弄清中性激子和中子的扩散对于理解使用TMDC使得新的光电器件架构的基本局限性和潜力至关重要。在这项工作中，我们测量中性激子和三重子在单层MoS中的扩散长度₂通过调谐用栅极电压和同时利用稳态和瞬态谱的背景载流子浓度。我们观察到在0.6 W cm ^–2的光功率密度下，中性激子和and的扩散长度分别为1.5μm和300 nm _。