Luminescence enhancement and Raman characterization of defects in WS2 monolayers treated with low-power N2 plasma

Abstract

In this work, WS2 monolayers synthesized by chemical vapor deposition submitted to low-power N2 plasma treatment for different periods of exposition, and its properties were studied by using a multi-technique approach. The results show that the photoluminescence signal from WS2 monolayers gradually increases for short treatment times and quenches for more extended periods of plasma exposure. Raman spectra of the treated WS2 monolayers also show that the E2g and A1g peak positions did not change significantly, suggesting that the treatment is not imposing a significant sort of mechanical strain or substantial lattice deformation. X-ray photoelectron spectroscopy (XPS) revealed the presence of N impurities incorporated into the lattice, while AFM confirms that for short treatment times, the sample keeps its integrity. Our results suggested that low-energy cold plasma treatment can be a reliable way to control WS2 optoelectronic properties.