First-Principles Study of Structural and Electronic Properties of MoS_1.5Se_0.5 Alloy

The effects of relative positions of Se atoms in a monomolecular layer of MoS1.5Se0.5 have been studied. It is demonstrated that the distribution of Se atoms between top and bottom chalcogen planes is most energetically favorable. For a more probable distribution of Se atoms this monolayer alloy is a direct semiconductor with the fundamental bandgap of 2.35eV. We have also evaluated the optical band gaps of the alloy at 77K (1.86eV) and room temperature (1.80eV), which are in a good agreement with the experimentally measured bandgap of 1.79eV.