Two-dimensional (2D) transition metal dichalcogenides (TMDCs) exhibit compelling dimension-dependent exciton-dominated optical behavior influenced by thickness and lateral quantum confinement effects. Thickness quantum confinement effects have been observed; however, experimental optical property assessment of nanoscale lateral dimension monolayer TMDCs is lacking. Here, we employ ex situ spectroscopic ellipsometry to evaluate laterally coalescing monolayer metalorganic chemical vapor deposited MoS₂. A multisample analysis is used to constrain Bruggeman and Maxwell–Garnett effective medium approximations and the effective dielectric functions are derived for laterally coalesced and uncoalesced MoS₂ films (∼10–94% surface coverage for ∼10–140 nm lateral grain sizes). This analysis demonstrates the ability to probe MoS₂ optical exciton behavior at growth-relevant grain sizes in relation to chemical vapor nucleation density, ripening, and lateral growth conditions. Our analysis is pertinent toward expected in situ epitaxial 2D TMDC film growth metrology to enable the facile development of monolayer films with targeted process-dependent optical properties.

中文翻译：

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横向聚结单层 MoS2 的有效光学性质

二维 (2D) 过渡金属二硫化物 (TMDC) 表现出引人注目的尺寸依赖性激子主导的光学行为，受厚度和横向量子限制效应的影响。已观察到厚度量子限制效应；然而，缺乏对纳米级横向尺寸单层 TMDCs 的实验光学性能评估。在这里，我们采用非原位光谱椭偏仪来评估横向聚结的单层金属有机化学气相沉积 MoS ₂。多样本分析用于约束 Bruggeman 和 Maxwell-Garnett 有效介质近似，并推导出横向聚结和未聚结 MoS _{2的有效介电函数}薄膜（~10-94% 的表面覆盖率，横向晶粒尺寸约为 10-140 nm）。该分析证明了在与化学气相成核密度、成熟和横向生长条件相关的生长相关晶粒尺寸下探测 MoS _{2光学激子行为的能力。}我们的分析与预期的原位外延 2D TMDC 薄膜生长计量学相关，以便能够轻松开发具有目标工艺相关光学特性的单层薄膜。