Unique optoelectronic properties of monolayer transition metal dichalcogenides (TMDs) originate from strong quantum confinement effects and reduced dielectric screening. However, their low dimensionality also renders photoinduced dynamics and the resulting properties highly susceptible to defects. Yet, the mechanistic relationship between intrinsic defects and non-uniform optoelectronic responses has remained elusive, calling for spatially resolved characterization to visualize heterogeneous photoinduced dynamics. Here, we apply ultrafast infrared scattering scanning near-field optical microscopy (ultrafast IR s-SNOM) to investigate WS₂ monolayers grown by chemical vapor deposition. We demonstrate that ultrafast IR s-SNOM, with the relatively high excitation fluence, sensitively probes the dynamics of electron–hole plasma induced in local domains of the individual WS₂ monolayers. The transient mid-infrared response is enhanced with extended lifetimes near the edges, indicating local mitigation of many-body interactions. We propose that the spatially modulated many-body dynamics is associated with defect-mediated mechanisms, providing implications for engineering TMD-based nanoscale optoelectronics.

中文翻译：

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CVD 生长单层 WS2 中空间调制多体动力学的超快纳米成像


单层过渡金属硫化物 （TMD） 的独特光电特性源于强量子限制效应和减少的介电屏蔽。然而，它们的低维数也使光诱导动力学和由此产生的特性极易受到缺陷的影响。然而，本征缺陷和非均匀光电响应之间的机理关系仍然难以捉摸，需要空间分辨表征来可视化异质光诱导动力学。在这里，我们应用超快红外散射扫描近场光学显微镜（超快 IR s-SNOM）来研究通过化学气相沉积生长的 WS₂ 单层。我们证明，超快 IR s-SNOM 具有相对较高的激发通量，可以灵敏地探测在单个 WS₂ 单层的局部域中诱导的电子空穴等离子体的动力学。瞬态中红外响应随着边缘附近寿命的延长而得到增强，表明多体相互作用的局部缓解。我们提出空间调制的多体动力学与缺陷介导的机制相关，为基于 TMD 的工程纳米级光电子学提供了启示。