MoS₂ Monolayers on Au Nanodot Arrays: Surface Plasmon, Local Strain, and Interfacial Electronic Interaction

Metal and transition-metal dichalcogenide (TMD) hybrid systems have been attracting growing research attention because exciton-plasmon coupling is a desirable means of tuning the physical properties of TMD materials. Competing effects of metal nanostructures, such as the local electromagnetic field enhancement and luminescence quenching, affect the photoluminescence (PL) characteristics of metal/TMD nanostructures. In this study, we prepared TMD MoS₂ monolayers on hexagonal arrays of Au nanodots and investigated their physical properties by micro-PL and surface photovoltage (SPV) measurements. MoS₂ monolayers on bare Au nanodots exhibited higher PL intensities than those of MoS₂ monolayers on 5-nm-thick Al₂O₃-coated Au nanodots. The Al₂O₃ spacer layer blocked charge transfer at the Au/MoS₂ interface but allowed the transfer of mechanical strain to the MoS₂ monolayers on the nanodots. The SPV mapping results revealed not only the electron-transfer behavior at the Au/MoS₂ contacts but also the lateral drift of charge carriers at the MoS₂ surface under light illumination, which corresponds to nonradiative relaxation processes of the photogenerated excitons.