Exploring the electronic, dynamic, thermal and optical properties of novel XS (X=Be, Mg, Ca and Sr) monolayer: A first-principles study

The electronic structure, dynamic, thermal, and optical characteristics of a hexagonal pure XS (where X = Be, Mg, Ca and Sr) monolayer are studied using DFT. These monolayers are structurally and thermally stable, according to AIMD simulations. At 300 K, there is no structural deformation, indicating XS monolayers are generally stable and preserved. Both BeS and MgS have indirect band gaps, but CaS and SrS have direct band gaps. The optical behaviors have been found to be anisotropic in the light polarized along the parallel directions. These results justify the usage of XS monolayers in thermal, photodetectors and other nanodevice applications.