Substrate-Induced Changes on the Optical Properties of Single-Layer WS₂

Among the most studied semiconducting transition metal dichalcogenides (TMDCs), WS (Formula presented.) showed several advantages in comparison to their counterparts, such as a higher quantum yield, which is an important feature for quantum emission and lasing purposes. We studied transferred monolayers of WS (Formula presented.) on a drilled Si (Formula presented.) N (Formula presented.) substrate in order to have insights about on how such heterostructure behaves from the Raman and photoluminescence (PL) measurements point of view. Our experimental findings showed that the Si (Formula presented.) N (Formula presented.) substrate influences the optical properties of single-layer WS (Formula presented.). Beyond that, seeking to shed light on the causes of the PL quenching observed experimentally, we developed density functional theory (DFT) based calculations to study the thermodynamic stability of the heterojunction through quantum molecular dynamics (QMD) simulations as well as the electronic alignment of the energy levels in both materials. Our analysis showed that along with strain, a charge transfer mechanism plays an important role for the PL decrease.