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

We report tip-enhanced Raman spectroscopy and tip-enhanced photoluminescence studies of monolayer and bilayer MoS2 in which we characterize photoluminescence and first- and second-order Raman spectra in monolayer, bilayer, and inhomogeneously strained MoS2. From the transition of unstrained MoS2 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 MoS2 that are directly observed through changes in the Raman peak positions and peak area ratios, which are corroborated through density functional theory calculations.