Photoluminescence quenching of CVD grown WS₂ monolayers treated with low-power Ar plasma

Defect engineering in two-dimensional materials is of high importance to improve a specific property of such materials. By introducing defects directly in the lattice, by means of ion doping or vacancies, it is possible to optimize the structure for a target application, such as high-performance batteries, catalysis, or optoelectronics. Herein, monolayer WS₂ was synthesized by chemical vapor deposition and was subsequently subjected to Ar plasma treatment. The changes in properties were monitored using Raman spectroscopy, photoluminescence (PL) spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy. The influence of defects resulted in a variation in the intensity of the PL signal, as well as a progressive redshift owing to an increase in the defect density with increasing plasma treatment time, and through the analysis of the PL and Raman spectra one can quantify the evolution of defects in the WS₂ monolayers due to the treatment.