The refractive index for pristine monolayer MoS₂ in the near-infrared is predicted to be ≥4. However, experimental literature reports n can decrease by ∼2 at energies below the band edge. In this work, we show variability in the optical response can correspond to changes in oscillator amplitude and dielectric polarizability of all measured excitons—suggesting exemplary charge transfer and local dielectric media effects discussed here are significant contributors in quantum nanophotonic interactions. Monolayer metal organic chemical vapor deposited MoS₂ films are evaluated herein using spectroscopic ellipsometry to assess changes in the refractive index (n) and extinction coefficient (k) due to dopant-induced screening effects from chemical adsorbates and mild film degradation. Notably, large reversible changes in the refractive index (Δn ≈ 2.2) are observed by varying n- and p-type chemical adsorbates. The extent of tailorable dopant-induced screening of MoS₂ optical constants illustrated in this work is also shown to be highly dependent on film quality. This suggests a dominant role of pre-existing structural defects on the optical properties of reported films to date. The tailoring of semiconducting transition metal dichalcogenide optical constants in a reversible manner is expected to have broad implications in the development of quantum optical and optoelectronic devices (e.g., high-precision engineered excitonic effects, electroabsorption modulators, and high-efficiency semiconductor nanophotonic technologies).

中文翻译：

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可逆地调整单层过渡金属二硫属化物 MoS ₂薄膜的光学常数：掺杂剂诱导的化学吸附物筛选和轻度薄膜降解的影响

原始单层MoS ₂在近红外区的折射率预计≥4。然而，实验文献报告n可以在低于带边的能量处减少~2。在这项工作中，我们展示了光学响应的​​可变性可以对应于所有测量激子的振荡器振幅和介电极化率的变化——这表明此处讨论的示例性电荷转移和局部介电介质效应是量子纳米光子相互作用的重要贡献者。单层金属有机化学气相沉积的 MoS ₂薄膜在本文中使用光谱椭偏法进行评估，以评估折射率 ( n ) 和消光系数 ( k ) 的变化。) 由于掺杂剂诱导的化学吸附物屏蔽效应和轻微的薄膜降解。值得注意的是，通过改变 n 型和 p 型化学吸附物可以观察到折射率的大的可逆变化 (Δ n ≈ 2.2)。MoS ₂的可定制掺杂剂诱导筛选的程度在这项工作中说明的光学常数也被证明高度依赖于薄膜质量。这表明预先存在的结构缺陷对迄今为止报道的薄膜的光学性能起主导作用。以可逆方式定制半导体过渡金属二硫属化物光学常数有望对量子光学和光电器件（例如，高精度工程激子效应、电吸收调制器和高效半导体纳米光子技术）的发展产生广泛影响。