Broadband optical properties of large-area monolayer CVD molybdenum disulfide

In this paper, we report a comprehensive study of fundamental optical properties of MoS sub(2) revealed by optical spectroscopy of Raman, photoluminescence, and vacuum ultraviolet spectroscopic ellipsome try. A band gap of 1.42 eV is determined by the absorption threshold of bulk MoS sub(2) that shifts to 1.83 eV in monolayer MoS sub(2). We extracted the high precision dielectric function up to 9.0 eV, which leads to the identification of many unique interband transitions at high symmetry points in the MoS sub(2) momentum space. The positions of the so-called A and B excitons in single layers are found to shift upwards in energy compared with those of the bulk form and have smaller separation because of the decreased interactions between the layers. A very strong optical critical point predicted to correspond to a quasiparticle gap is observed at 2.86 eV, which is attributed to optical transitions along the parallel bands between the M and [Gamma] points in the reduced Brillouin zone.