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 365-1700nm. 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.