Spectroscopic Study of the Excitonic Structure in Monolayer MoS2 under Multivariate Physical and Chemical Stimuli

Photoluminescence (PL) spectroscopy has proven to provide deep insights into the optoelectronic properties of monolayer MoS2$\left(\text{MoS}\right)_{2}$. Herein, a corresponding study is conducted on the excitonic properties of mechanically exfoliated monolayer MoS2$\left(\text{MoS}\right)_{2}$ under multivariate physical and chemical stimuli. Specifically, midgap exciton states that originate from lattice defects are characterized and they are compared to existing models. Through statistical data analyses of substrate‐, temperature‐, and laser‐power‐dependent measurements, a PL enhancement is revealed through physisorption of water molecules of the controversially discussed excited‐state A biexciton (AXX*$A^{\left(\text{XX}\right)^{\star}}$). In addition, analyses of monolayer MoS2$\left(\text{MoS}\right)_{2}$ on gold substrates show that surface roughness does not account for changes in doping level within the material. Also, a shift in the electron–phonon coupling properties that arises from thin films of water that are physisorbed on top of the samples is reported. This photoluminescence study examines excitonic properties of monolayer MoS2 through physical and chemical stimuli. It reveals midgap states originating from lattice defects alongside their characteristics and compares them to existing models. Statistical analyses show that the physisorption of water enhances the excited‐state A‐biexciton's photoluminescence and changes the electron–phonon coupling properties, and gold's surface roughness does not impact the doping level.