Probing Sulfur Vacancies in CVD-Grown Monolayer MoS2 on SiO2/Si in the Temperature Range 750–900°C

Abstract

This work reports morphologically alike, high-quality monolayer MoS2 flakes with a similar strain at various growth temperatures (750–900°C) achieved by adjusting sulfur temperature. The growth dynamics of MoS2 are correlated with changes in the photoluminescence (PL) and Raman peak positions. Monolayer MoS2 crystals are synthesized at different growth temperatures from 750°C to 900°C using chemical vapor deposition (CVD). We examined the structural quality and aimed to extract the recombination mechanisms in MoS2 using low-temperature, variable, and low-laser-intensity PL measurements. Our studies of the defect-associated bound exciton emission are well correlated with the blueshift in the A1g mode of Raman spectra, blueshift in PL spectra, and x-ray photoelectron spectroscopy results for crystal grown at 900°C. Our research findings not only shed light on a thorough, non-intrusive method for modifying growth parameters to enhance optical performance, but they also suggest a way to modify the optical characteristics of MoS2 while maintaining the morphology.

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

“…On the other hand, since oxygen is isovalent to sulphur, chemisorption of oxygen (during synthesis process) is expected to passivate sulphur vacancies without significantly modifying the crystal structure, and thus improve the optoelectronic quality of the sample [16][17][18][19]. Also, the increased biaxial tensile strain in CVD samples due to the high synthesis temperature could induce a peak shift, and increase or decrease the PL intensity, depending upon the type and amount of strain present [10,11,26].…”

Activating Nitrogen for Electrochemical Ammonia Synthesis via an Electrified Transition-Metal Dichalcogenide Catalyst

“…14,17 MoS 2 is naturally sulfur vacancy defect rich, with chemical vapor deposition and exfoliation methods yielding defect densities of the order 1 × 10 13 cm −2 . 51,52 Additionally, there are several methods to experimentally tune the sulfur defect density of MoS 2 , including modifying the growth conditions, 53 postgrowth desulfurization techniques such as Ar plasma exposure, 54 H 2 annealing, 55 and electrochemical desulfurization (at reductive potentials of at least −1 V vs RHE), 56 as well as postgrowth defect healing. 57 Figure 2 shows the model system for this work and denotes the molybdenum nonvacancy (Mo NV ) and surface sulfur sites (S) that we determined are inactive.…”