Photoluminescence Quenching and SERS in Tri-layer MoS2 Flakes

In this paper, we report photoluminescence (PL) and surface-enhanced Raman spectroscopy of atomically thin molybdenum disulphide (MoS2) on SiO2/Si substrate grown by chemical vapor deposition. We investigated the impact of Ag and Au nanostructure on the surface of MoS2 film through PL and Raman spectrum. Apart from enhanced Raman scattering, a heavy fall in PL intensity was observed because of the charge transfer from MoS2 to the metal hybrid structure. To support this, the work function was estimated by Kelvin probe force microscopy, and it was found to be 4.27 eV on pristine MoS2 film and 4.75 eV and 4.86 eV with the use of Ag and Au nanostructures separately on MoS2 film. Furthermore, using one-dimensional Schrödinger–Poisson (1D-SP) simulations, the band diagram and carrier concentration of molybdenum disulphide before and after the metal contact has also been calculated. The change in work function and more than hundred times decrease in carrier concentration explains the quenching of PL intensity due to charge transfer. Moreover, the results indicate the enhancement in Raman intensity due to local surface plasmon resonance of Au and Ag nanoparticles.