Tip-Enhanced Raman Scattering on Bulk MoS2 Substrate

Surface-enhanced Raman scattering (SERS) has many applications in nanotechnology, biophotonics, and sensing. Conventional SERS is based on surface plasmon resonances of noble metal nanostructures that enhance molecular Raman signals via electromagnetic mechanism and on molecule–substrate interaction via chemical mechanism. Recent studies used 2-D materials as atomically flat SERS substrates based on the chemical mechanism. Here, we use tip-enhanced Raman scattering (TERS) to enhance Raman signals from copper phthalocyanine molecules deposited on a bulk MoS
₂
substrate by a nanosized gold tip via electromagnetic enhancement. We present a comparative study of MoS
₂
, gold, and SiO
₂
substrates. MoS
₂
changes relative intensities of molecular vibrations and provides additional gap-mode enhancement of TERS via interaction with the gold tip. Our results can be used to improve sensitivity and resolution in single molecule detection and imaging on flat substrates.