Synthesis and ellipsometric characterizations of large-scale MoS2 sub-monolayer

Two-dimensional (2D) transitional metal dichalcogenides (TMDs) have drawn significantly interest motivated by their prominent properties for electronics beyond silicon. Despite extensive efforts, continuous TMDs monolayer films are still difficult to grow with high yield, and universal characterization methods potential for industrial mass production are lacking, which significantly hinder their applications. Here, we designed a controllable chemical vapor deposition method to directly synthesis high-quality and large-scale MoS2 monolayer with various surface coverage ratios (CRs), representing growth stages from nucleation to connected film. A series of optical characterization methods and dielectric analysis were conducted to systemically study the monolayer feature of MoS2. Then, we demonstrated an alternative characterization strategy by disclosing the relations of measured Spectroscopic Ellipsometry (SE) spectra Δ and Ψ to the CRs of MoS2 sub-monolayer, achieving a direct model-free assessment. The SE spectra show extraordinary sensitivity to the sub-monolayer CRs. This work presents a paradigm to generally evaluate large-scale 2D materials and offers basic SE characterization toward industrial production.