Figure 5.

Raman and photoluminescence spectroscopy results. (a, b) Raman spectra of the untreated (pristine) and plasma-treated samples of WS₂ (one plasma process—a, two plasma processes—b). The treatment of the samples resulted in the asymmetric shift of the two main peaks (upshift of A_1g, downshift of E¹_2g), changing the difference in peaks’ positions (Δpos A_1g–E_2g). (c, d) Photoluminescence spectra of WS₂ untreated and treated samples. The plasma treatment resulted in the signal quenching and the blue shift of the peaks by Δpos PL = 0.0034 eV (c) after the first plasma process and 0.0043 eV (d) after the second plasma process. The position of the peak was calculated as the mean value of the two fitted Lorentzian curves.