Spectral ellipsometry of monolayer transition metal dichalcogenides: Analysis of excitonic peaks in dispersion

Optical constants of monolayers MoS2 and WS2 were measured by spectroscopic ellipsometry in the spectral range 365–1700 nm. Analysis of ellipsometry spectra was carried out, taking into account the excitonic nature of dispersion. In the considered wavelength range, excitons originate from different interband transitions. As a result, they can be described via Tauc–Lorentz oscillators, one for each exciton. The scalability and universality of such an approach could be applied for the extended wavelength range and to the other transition metal dichalcogenides.