Nano-Raman imaging of monolayer MoS2 nanoribbons

Abstract

Two-dimensional semiconductors are promising candidates for next-generation electronics. However, characterizing these materials at technologically relevant dimensions remains underexplored. Here, we use tip-enhanced Raman spectroscopy (TERS) to map lithographically-patterned monolayer MoS2 nanoribbons down to 50 nm widths. The surface sensitivity of TERS enables direct nanoscale assessment of the MoS2 surface after a vacuum annealing procedure that removes resist residues. Subsequently, we find a consistently strong TERS response across the nanoribbon, indicating good quality MoS2 and a clean interface to the Au substrate. The good spatial resolution of TERS (down to ∼10 nm) uncovers small, 50–100 nm regions of inhomogeneities, likely arising from the growth process with a higher intensity and redshifted 2LA(M) peak. We also find a 0.5 cm−1 redshift of the A1′ mode at nanoribbon edges, consistent with a fixed negative charge. Our study highlights how advanced nanoscale metrology can be leveraged for future devices and fabrication process optimization.