Metal mono-chalcogenides ZnX and CdX (XÂ =Â S, Se and Te) monolayers: Chemical bond and optical interband transitions by first principles calculations

In this paper, we explore the structural, electronic and optical properties of ZnX and CdX (X = S, Se and Te) compounds in the two-dimensional (2D) graphene-like structure using the full potential augmented plane waves plus local orbitals (FP-APW+lo) method. Unlike their bulk phase, they are optically inactive because of their indirect band gap nature except CdS and ZnS. These two compounds maintain their direct band gap nature and hence are optically active. The static dielectric constants for these monolayers illustrate increasing trend with decrease in the band gap values. Furthermore, an acceptable description of electron transitions in these monolayers is accomplished according to the imaginary parts of the dielectric functions and absorption spectra in ZnS and CdS as examples of each group of CdX and ZnX. The results presented in this article revealed that ZnS and CdS in the 2D structure can be effectively used in optoelectronic devices such as solar cell materials and so forth.