The Influence of Point Defects on the Electronic and Magnetic Properties of WS2 Monolayer Based on Density Functional Theory

The present study investigates the effect of point defects in the structure of monolithic tungsten disulfide (WS2) using basic principles. This study was performed on six vacancies to investigate their effects on the electronic and magnetic properties of WS2 monolayer. The structure under study was a supercell with 36 atoms and the atomic positions were optimized. In the present study, density functional theory calculations were performed within the framework of local density approximation. Structural analysis of this material showed that the WS2 monolayer had a direct band gap of 1.89 eV. The simulation results illustrated that depending on the type of defects in the structure and their position, the behavior of the structure can change from semiconductor to quasi-metal and non-magnetic to magnetic. For instance, the removal of one tungsten atom leads to the metallization and magnetization of the structure. Moreover, the bandgap energy of the WS2 monolayer decreased in the absence of one sulfur atom.  In addition, there was a transition from direct to indirect semiconductors and a reduction in the energy of the band gap in comparison with its pristine. These cases indicate that the presence of defects in semiconductor nanostructures paves the way for the application of such nanostructures in tunable electronics, optical electronics, and spintronics.