Facile Projection of Spatially Resolved Refractive Index Modulation in Monolayer MoS₂ via Light Phase Changes

Fast spatial contouring of the complex refractive index (n  +  ik) of semiconducting materials is a much sought-after goal since the advent of semiconductor-related industries. This study develops a novel metrology to shape the refractive index modulation of materials using hyperspectral phase microscopy by maximizing the light-matter interaction of physical properties. The facile, non-destructive, and wide-field hyperspectral phase technique realizes efficient visualization of the spatially resolved refractive index nature induced by strain within and among examined MoS₂ materials. Furthermore, numerical analyses based on a steady-state transfer matrix clarify that the spectral phase difference (Δϕ) is selectively sensitive to the modulation of refractive index (n) but not of extinction coefficient (k) under certain wavelength ranges. This dependence is associated with wavelength and the thickness of the dielectric layer on the substrates. Simple linear relation between n and Δϕ for ≈100 nm of SiO₂, dielectric material supporting MoS₂, enables to visualize the excitonic A and B band modulation, and furthermore, refractive index with fairly high precision (coefficient of determination, R² > 0.97 in the wavelength range of 530-630 nm).