Understanding the ultrafast carrier dynamics of transition metal dichalcogenides is critical for future applications in high-speed electronic and optoelectronic devices. In this work, we used a combination of femtosecond (fs) time-resolved micro-area photoelectron spectroscopy and photoemission electron microscopy (PEEM) to obtain the space-resolved surface photovoltage (SPV) and photoelectron intensity dynamics of two-dimensional (2D) molybdenum disulfide (MoS₂) flakes, both of which exhibited high spatial heterogeneity and defect effects. Additionally, surface S vacancy defects were characterized by spatially resolved X-ray photoelectron spectroscopy. The SPV relaxation dynamics indicated that the charge carrier lifetime in the space-charge layer (SCL) ranged from several to tens of nanoseconds and was dominated by the thermionic emission process. The defects, which acted as electron-hole recombination centers, greatly shortened the charge carrier lifetime by almost one order of magnitude. Furthermore, three relaxation processes were observed in the photoelectron intensity dynamics, namely, two fast processes with rates of 3–6 ps (ps) and 60–100 ps, which were largely affected by the defect density, and one slow relaxation process with a rate of 2–5 ns (ns). However, these were not related to the defect density and were attributed to the transportation of electrons towards the bulk. Therefore, our results provide a deeper understanding of the interfacial carrier dynamics of 2D-MoS₂ materials and the effects of defects on charge carrier lifetime in the SCL.

了解过渡金属二硫属化物的超快载流子动力学对于未来在高速电子和光电器件中的应用至关重要。在这项工作中，我们结合使用飞秒 (fs) 时间分辨微区光电子能谱和光电电子显微镜 (PEEM) 来获得二维 (2D) 的空间分辨表面光电压 (SPV) 和光电子强度动力学。二硫化钼（MoS ₂）薄片，两者都表现出高度的空间异质性和缺陷效应。此外，表面S空位缺陷的特征在于空间分辨 X 射线光电子能谱。SPV 弛豫动力学表明空间电荷层 (SCL) 中的电荷载流子寿命从几纳秒到几十纳秒不等，并且受热电子发射过程支配。这些缺陷作为电子-空穴复合中心，大大缩短了电荷载流子寿命几乎一个数量级。此外，在光电子强度动力学中观察到三个弛豫过程，即两个速率为 3-6 ps (ps) 和 60-100 ps 的快速过程，这在很大程度上受缺陷密度的影响，以及一个慢弛豫过程2–5 ns (ns) 的速率。然而，这些与缺陷密度无关，而是归因于电子向体的传输。所以，₂材料和缺陷对 SCL 中电荷载流子寿命的影响。