Tip-Enhanced Raman Spectroscopy of Monolayer MoS₂ on Au(111)

Abstract

Employing gap-mode plasmons in a scanning tunneling microscope junction, we studied tip-enhanced Raman spectroscopy (TERS) of MoS 2 on Au(111). We observed a mode denoted as "m", positioned to the right of A 1 ′ by a difference of approximately 6 cm −1 . In the MoS 2 region that is not in direct contact with the Au(111) substrate, the m peak still exists, indicating that the m mode originates from MoS 2 . The m mode could originate from non-Γ-point phonon modes in the ZO branch or LA(K) + TA(K). Additionally, our investigation reveals that the TERS intensity reaches its maximum by continuing to approach MoS 2 after the tip contacts MoS 2 . The tip displacement required to reach the maximum TERS intensity depends on the tip conditions. Our results provide guidance for obtaining the optimal TERS intensity for MoS 2 and have potential application to other two-dimensional transition metal dichalcogenides.