Fig. 5

Effect of the edge structure on the peak position of the Raman A_1g mode. (a) Typical line-trace TERS spectra of the zigzag edge (left panel) and armchair edge (right panel) in the spectral range of the A_1g mode. Note that the spectra have been normalized with the intensity of A_1g peak for a better comparison. (b) Plots of peak position with the tip position. The corresponding line-trace TERS spectra are shown in Supplementary Fig. 16a and Supplementary Fig. 20a, respectively. The dash red lines are guides for the eye. (c) Calculated Raman spectra and lattice vibration of the basal plane, zigzag nanoribbon (ZNR, with a width of 3.59 nm) localized at the Mo and S edges, and armchair nanoribbon (ANR, with a width of 2.05 nm). The envelope of each Raman spectrum is evaluated by smearing the peaks with half width 5 cm⁻¹. Note that the displacements of A_1g or A_1g-like mode with out-of-plane vibration are side viewed. See Supplementary Note 3.4 for details. (d) AFM image of a mechanically exfoliated 1 L MoS₂ with different edge angles on an Au substrate. (e) Illustration of the relationship between angles and edge structures of zigzag (ZZ) and armchair (AC) in 2 H MoS₂. (f) TERS spectra of four edges in the spectral range of the A_1g mode marked in d. Note that the spectra have been normalized with the intensity of A_1g peak for a better comparison. The corresponding line-trace TERS spectra of these edges are shown in Supplementary Fig. 22.