Effects of contact material on complex excitonic behaviour of monolayer MoS2

We investigated the optical behaviour of excitons in monolayer MoS2 prepared on a 60 nm-thick metal (Au) ring structure patterned on SiO2. CVD-grown monolayer MoS2 was transferred to the metal structure and placed in contact with three different environments simultaneously: SiO2, Au metal and air. The optical properties of the transferred MoS2 on the substrates were characterized through micro-photoluminescence (mu-PL) measurements. PL peaks were observed near similar to 1.82 eV for defect-related emission, similar to 1.92 eV for an A exciton, which includes a neutral exciton and a trion, and similar to 2.1 eV for a B exciton. The optical band gap and exciton-phonon interaction of the samples on the three substrates were investigated by measuring the temperature-dependent photoluminescence.