Probing nanoscale variations in strain and band structure of MoS2 on Au nanopyramids using tip-enhanced Raman spectroscopy

Abstract

We report tip-enhanced Raman spectroscopy and tip-enhanced photoluminescence studies of monolayer and bilayer $\mathrm{Mo}{\mathrm{S}}_{2}$ in which we characterize photoluminescence and first- and second-order Raman spectra in monolayer, bilayer, and inhomogeneously strained $\mathrm{Mo}{\mathrm{S}}_{2}$. From the transition of unstrained $\mathrm{Mo}{\mathrm{S}}_{2}$ from monolayer to bilayer, we determine a spatial resolution of approximately 100 nm through the peak positions of the first-order Raman modes. The strain dependence of the second-order Raman modes reveals changes in the electronic band structure in strained $\mathrm{Mo}{\mathrm{S}}_{2}$ that are directly observed through changes in the Raman peak positions and peak area ratios, which are corroborated through density functional theory calculations.