First-Principles study on electronic structure and optical properties of monolayer Mo1-xMx(M = W or Cr)S2

Abstract

Two-dimensional transition metal dichalcogenides (TMDCs) such as MoS2 has potential applications in electronics and photonics. Here, we theoretically improve the properties of MoS2 through substituting Mo with isovalent W or Cr. The crystal structure, electronic structure, and optical properties of Mo1-xMx(M = W or Cr, x = 1/16)S2 were calculated by First-Principles methods in our work, the relationship between the MoS2 and Mo15/16M1/16S2 was investigated. The results show that MoS2 and Mo15/16W1/16S2 have similar crystal parameters, while the CrS bond length was smaller than MoS significantly and the SCrS and SWS bond angles are slightly smaller than the SMoS bond angle. The calculated electronic properties results show that W has almost no effect on the band gap of MoS2, while the band structure of Mo15/16Cr1/16S2 changed from direct to indirect and the band gap reduced significantly. The electrons in Mo-4d and S-3p orbitals made greater contributions to the valence band maxima (VBM) and conduction band minima (CBM), the electrons in W-5d or Cr-3d orbitals also have contribution to the electronic structures. Meanwhile, the calculated results of optical properties show that the imaginary part of dielectric functions of Mo15/16W1/16S2 blue-shifted and Mo15/16Cr1/16S2 red-shifted compared with MoS2, the trend of absorption coefficient and reflectivity of the three materials is similar with the imaginary part of dielectric function in the low energy region.