Variable angle spectroscopic ellipsometry characterization of spin-coated MoS2 films

In the field of Transition Metal Dichalcogenides (TMDCs), molybdenum disulfide (MoS2) has attracted an outstanding interest thanks to several applications. MoS2 has potentialities not yet fully realized in solution-based applications. However, the lack of knowledge of the optical properties of MoS2, especially in the infrared range, has significantly limited his use in many exciting photonic fields. In this work, the broadband optical properties of MoS2 films deposited by spin-coating onto Si/SiO2 substrates were studied by means of Variable Angle Spectroscopic Ellipsometry (VASE). The morphological and the structural properties of the samples were investigated by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Micro-Raman Spectroscopy. Micro-Raman spectroscopy measurements reveal the presence of 2H-MoS2 and 1T-MoS2 phases. The optical properties of the films show a mid-gap state at~ 0.6 eV, not reported in an ellipsometry work before, induced by defects in the MoS2 samples.