Probing the Effect of Chemical Dopant Phase on Photoluminescence of Monolayer MoS₂ Using in Situ Raman Microspectroscopy

Abstract

Understanding the role of chemical dopants is crucial to modulating the optoelectronic properties of monolayer (ML) MoS2 and realizing its optoelectronic applications such as photodetectors, switching devices, and ultrathin transistors. Here, the effect of the dopant phase of the same dopantsliquid and gaseouson the optical properties of ML MoS2 has been investigated using in situ Raman microspectroscopy with an environment-controlled reaction cell. The results show that the gaseous n-type dopant, that is, pyridine, completely quenched the PL intensity of ML MoS2, while liquid pyridine preserved 50% of the original PL intensity attributed to its less effective charge transfer to MoS2 than the gaseous counterpart. Photoemission of the quenched MoS2 could not be recovered with mild annealing in nitrogen and only partially recovered upon long-term exposure to air. The results show that the dopant phase strongly impacts the PL properties of ML MoS2.

Stabilizing the heavily-doped and metallic phase of MoS2 monolayers with surface functionalization

“…The initial 2H MoS 2 (transferred onto ITO) demonstrates the highest PL intensity at ∼680 nm and corresponds to emission from the A exciton [34]. The A exciton emission is quenched when the monolayers are treated with BuLi for 30 mins, which is similar to previous n-type doping experiments [34,55]. However, the PL grows in when the n-type doped 2H phase MoS 2 monolayers are exposed to air.…”

Different healing characteristics of thiol-bearing molecules on CVD-grown MoS2

“…PL measurements were performed to investigate the effect of the chemisorbed molecules on the optical band gap of MoS 2 [31,32] and on the excitonic recombination processes, which are sensitive to the charge carrier density [33,34]. Figure 5 presents the PL spectra of both as-grown and annealed samples before and after functionalisation; the spectra show an intense peak located at a photon energy of about 1.85 eV and a minor feature at 2.00 eV that can be attributed respectively to the A and B excitons arising from the splitting of the valence band [35,36].…”

Room‐Temperature Low‐Voltage Control of Excitonic Emission in Transition Metal Dichalcogenide Monolayers

“…The observed deviation might be due to additional quenching processes taking place at high doping densities, such as non‐radiative Auger recombination and charge screening by the ITO electrode and the electrolyte. [ 40 ] Eventually, the charged exciton dominated in the photoluminescence signal after the Fermi level was increased above the bottom of conduction band for both WSe 2 and WS 2 .…”