Amplified Local Strain Signal in Strain-Plasmonic Coupled van der Waals Heterostructures

Strain engineering is a promising method for improving the optical and optoelectrical properties of two-dimensional (2D) materials. However, the local strain applied by the patterned substrate is highly localized, resulting in a small average local strain that can be detected using traditional optical methods. Here, we report a simple strategy to efficiently amplify the local-strain signal of 2D materials, by mechanically integrating monolayer ${\mathrm{Mo}\mathrm{S}}_{2}$ on $\mathrm{Au}$ nanoparticles of predetermined size. Using Raman and photoluminescence measurements, it is proved that ${\mathrm{Mo}\mathrm{S}}_{2}$ wrapped around $\mathrm{Au}$ nanoparticles with an average diameter of 39 nm can achieve the strongest strain-plasmonic coupling. Within this structure, the significant amplification effect of plasmonic coupling on the local strain signal is studied in detail by Lorentzian fitting of the Raman and PL spectra. The detected maximum local strain signal can reach 2.78%, and the corresponding local strain signal is amplified by more than 650%. Furthermore, the physical mechanism of local-strain-signal amplification is analyzed due to the robust strain-plasmonic coupling. This result provides a simple method for amplifying the local strain signal, paving the way for high-performance 2D optical and optoelectronic devices. This method provides a structure to amplify the local strain signal combined with plasmonic coupling, which can promote the development of high-performance broadband photodetectors.