Energy control of strain-induced localized states in a WS ₂ monolayer

Strain engineering has become a key method for tuning the optical properties of two-dimensional transition metal dichalcogenides by deforming their crystal lattice. In this study, we demonstrate how localized strain engineering can enhance trion emission at precise points with maximum strain, by using nanopillar arrays. At room temperature, by applying non-homogeneous biaxial strain, we create a potential energy landscape that efficiently converts excitons into trions, resulting in a well-defined two-peak structure in the photoluminescence (PL) spectrum. At cryogenic temperature, we observe sharp localized emission peaks, indicating highly confined excitons at strained lattice sites. By comparing strain-induced emitters at nanopillar sites with random native defects, we experimentally demonstrate that strain can effectively control the density and emission energy of localized emitters, providing a pathway for the deterministic formation of localized emitters with precise energy.