Effect of disorder on Raman scattering of single-layer MoS2

We determine the effect of defects induced by ion bombardment on the Raman spectrum of single-layer molybdenum disulfide. The evolution of both the linewidths and frequency shifts of the first-order Raman bands with the density of defects is explained with a phonon confinement model, using density functional theory to calculate the phonon dispersion curves. We identify several defect-induced Raman scattering peaks arising from zone-edge phonon modes. Among these, the most prominent is the LA(M) peak at similar to 227 cm(-1) and its intensity, relative to the one of first-order Raman bands, is found to be proportional to the density of defects. These results provide a practical route to quantify defects in single-layer MoS2 using Raman spectroscopy and highlight an analogy between the LA(M) peak in MoS2 and the D peak in graphene.