with point defects*

Point defects in single-layer transition-metal dichalcogenides (TMDs) are common, and point defects in layered TMDs – including vacancies and chemical substitutions – have been reported to affect their electronic structure and photophysics. Here, we use first-principles density functional theory and the GW and GW-BSE calculations to explore the structure and the tunneling and optical properties of substitutional points defects in monolayer tungsten disulfide. Using a large supercell, we compute the atomic structure, quasiparticle band structure, defect states, and low-lying excitons for dilute defect concentrations. We compare our structure and quasiparticle excitation spectrum with state-of-the-art non-contact atomic force microscope and scanning tunneling spectroscopy measurements.