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 $\mathrm{LA}\left(M\right)$ peak at $\sim 227\mathrm{c}{\mathrm{m}}^{-1}$ 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 $\mathrm{Mo}{\mathrm{S}}_2$ using Raman spectroscopy and highlight an analogy between the $\mathrm{LA}\left(M\right)$ peak in $\mathrm{Mo}{\mathrm{S}}_2$ and the $D$ peak in graphene.

• Received 26 January 2015

DOI:https://doi.org/10.1103/PhysRevB.91.195411