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

Among the most studied semiconducting transition metal dichalcogenides (TMDCs), WS2 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 WS2 on a drilled Si3N4 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 Si3N4 substrate influences the optical properties of single-layer WS2. 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.

Automated summary

In this study, the behavior of monolayer WS2 on a drilled Si3N4 substrate was investigated through Raman spectroscopy and photoluminescence measurements. It was found that the Si3N4 substrate affects the optical properties of monolayer WS2. Density functional theory and quantum molecular dynamics simulations showed that strain and charge transfer mechanism are important factors for the decrease in photoluminescence.