A wafer-scale method for the characterization of 2D MoS2 layers

Wafer-scale deposition of 2D TMDs (Transition Metal Dichalcogenides) is a key point for their integration in future devices. While significant efforts have been dedicated to improving the quality and uniformity of 2D materials, their implementation requires a robust characterization protocol to assess the surface coverage, layer number, stoichiometry, homogeneity, crystallinity and morphology. In this work, we developed a characterization protocol that combined local analyses and large-scale methods. This protocol was applied to MoS₂ films grown on SiO₂ substrate by Atomic Layer Deposition (ALD) using two different precursors, enabling the determination of the number of ALD cycles required to achieve a strict monolayer with full wafer-scale coverage. Atomic Force Microscopy (AFM), X-ray Photoelectron Spectroscopy (XPS), and Scanning Transmission Electron Microscopy (STEM) provided insights into composition, surface coverage and equivalent thickness from sub-monolayer to above-monolayer thickness range at low scale. The combination of Wavelength-Dispersive X-ray Fluorescence (WDXRF), Scanning Electron Microscopy (SEM), Raman spectroscopy and Photoluminescence, enables a rapid and accurate evaluation of the uniformity at wafer scale, the equivalent thickness and composition of TMD films across the wafer.