Characterization of wafer-scale MoS2 and WSe2 2D films by spectroscopic ellipsometry

Here, we present the spectroscopic ellipsometry investigation of synthetically grown wafer-scale two-dimensional (2D) MoS2 and WSe2 films to access quality and thickness uniformity. MoS2 and WSe2 samples were grown by chemical vapor deposition and atomic layer deposition, respectively. Complex dielectric function (ε=ε1+iε2) and thickness information of these 2D films were extracted from the measured data using multilayer optical calculations. Broad spectral range (1.2-6 eV) and multiple angles of incidence were used to reduce correlations among fitting parameter. Lineshape of ε of MoS2 and WSe2 monolayer films are consistent with literature but shows higher values, suggests better quality of our samples. Eight-inch wafer size MoS2 monolayer sample shows ∼ 70% uniformity with an average thickness of 0.65 ± 0.2 nm, and three-layer WSe2 sample of 8 × 1 cm2 area shows ∼ 80% uniformity with an average thickness of 2.5 ± 0.4 nm. Our results will be helpful to accelerate commercialization process of 2D devices.