Ab-initio study of the optical properties of beryllium-sulphur co-doped graphene

Graphene is a carbon material with excellent properties, which makes it applicable in a myriad of applications. However, the range of the applications of graphene can be extended to the developing field of nanoelectronics and optoelectronics by doping it with heteroatoms. In this study, Be and S atoms were used to co-dope graphene. The impurity concentration was varied by increasing the size of the supercell from 2x2 through 4x4. First-principles calculations were performed to determine the dynamic stability, band structure, and optical characteristics of the system. The results of the phonon dispersion of beryllium and sulphur co-doped graphene (Be-S) show the absence of imaginary modes, suggesting that Be-S is dynamically stable. The analysis of the band structure indicates that it has a tunable indirect band-gap which increases with the impurity concentration. A band-gap magnitude is required in a graphene-based transistor. Thus, Be-S could be considered as a transistor material. As regards with the optical properties, it is observed that the optical transparency of the graphene in the ultraviolet region changes with the impurity concentration. The result shows that Be-S can be used to manipulate light waves for a device application.