Tip-Enhanced Raman Spectroscopy and Tip-Enhanced Photoluminescence of MoS2 Flakes Decorated with Gold Nanoparticles

Monolayers and a few layers of transition metal dichalcogenides (TMDs), organized asflakes orfilms, are notable fortheir electronic and optical properties, highlighting their interest for a variety of applications. Specifically, MoS2flakes andfilms showa direct bandgap in their 2D form, which opens to applications in energy storage, optoelectronic devices, and in biosensingapplications. Interestingly, hybrid systems composed of MoS2flakes interfaced with metal nanoparticles, such as gold and silver,exploit the interplay between the interaction of plasmon of the metallic nanoparticle and the exciton of MoS2. Such plasmon-exciton interaction can be exploited to further improve the efficiency of TMD-based applications for sensing, catalysis, andphotovoltaics. In this work,flakes of MoS2grown on SiO2/Si substrates were prepared by chemical vapor deposition (CVD) underambient pressure and were subsequently decorated using gold nanoparticles of distinct sizes. Tip-enhanced Raman spectroscopy andtip-enhanced photoluminescence measurements as well as contact potential difference (CPD) were conducted to evaluate theplasmon-exciton coupling of MoS2flakes decorated with raspberry-like (similar to 100 nm) and seed-like (similar to 20 nm) gold nanoparticles.