Strain-Induced Sulfur Vacancies in Monolayer MoS₂

The tuning of two-dimensional (2D) materials offers significant potential to overcome nanoelectronic limitations. As strain engineering is a nondestructive approach, we examine in this study the influence of biaxial strain on the chalcogen vacancy formation energy in transition metal dichalcogenides, employing a combination of calculations and experiments, specifically density functional theory, spherical-corrected scanning transmission electron microscopy, X-ray photoelectron spectroscopy, Raman and photoluminescence spectroscopy, Kelvin probe force microscopy, and I-V characterization. We demonstrate that compressive/tensile biaxial strain decreases/increases the chalcogen vacancy formation energy, increasing/decreasing the probability of creating chalcogen vacancies during the growth. Thus, differently strained areas within a sample can have different chalcogen vacancy densities, opening up a way to customize the work function and a route for defect engineering.