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

Abstract

Photoluminescence (PL) spectroscopy has proven to provide deep insights into the optoelectronic properties of monolayer . Herein, a corresponding study is conducted on the excitonic properties of mechanically exfoliated monolayer 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 (). In addition, analyses of monolayer 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.

Understanding the interplay of defects, oxygen, and strain in 2D materials for next-generation optoelectronics

“…Further, the total PL intensity from the samples increases as the temperature is lowered, due to reduced phonon interactions (reduced scattering out of the light cone) and nonradiative recombination (carrier scattering) [29]. The blueshift in peak position with the temperature is due to an increase in the bandgap, as observed for most semiconductors [30][31][32]. For all samples, the linewidth of the A-exciton reduces with the temperature due to the reduced phonon-induced homogeneous broadening.…”

Photoluminescence Enhancement of Monolayer WS2 by n-Doping with an Optically Excited Gold Disk

“…Here, the dots correspond to the measured data, and the solid lines are the total fitted curves, with filled curves representing the individual excitonic components. We use the PLinterafit Python package , to fit Voigt functions to our measured data and statistically analyze the quality of our fit. Based on our analysis with two and three Voigt functions, we concluded that we cannot describe the PL measurements with acceptable goodness-of-fit values using only Voigt functions.…”

“…Here, the dots correspond to the measured data, and the solid lines are the total fitted curves, with filled curves representing the individual excitonic components. We use the PLinterafit Python package 40,41 to fit Normalized difference reflection (DR) spectra from measurements (dots) and normalized cross sections from simulations (solid lines). The scattering (σ sca ) and absorption (σ abs ) cross sections of the hybrid system are shown as black and red solid lines, respectively.…”

“…The population of A XX increases with that of A 1s . , It could also be that the A – emission is suppressed by the Au-disk through the dielectric-screening effect. It has been shown both experimentally and theoretically that the relative trion population decreases due to the dielectric screening. − …”