Strain-Plasmonic Coupled Broadband Photodetector Based on Monolayer MoS2.

2D Semiconductors are promising in the development of next-generation photodetectors. However, the performances of 2D photodetectors are largely limited by their poor light absorption (due to ultrathin thickness) and small detection range (due to large bandgap). To overcome the limitations, a strain-plasmonic coupled 2D photodetector is designed by mechanically integrating monolayer MoS2 on top of prefabricated Au nanoparticle arrays. Within this structure, the large biaxial tensile strain can greatly reduce the MoS2 bandgap for broadband photodetection, and at the same time, the nanoparticles can significantly enhance the light intensity around MoS2 with much improved light absorption. Together, the strain-plasmonic coupled photodetector can broaden the detection range by 60 nm and increase the signal-to-noise ratio by 650%, representing the ultimate optimization of detection range and detection intensity at the same time. The strain-plasmonic coupling effect is further systematically characterized and confirmed by using Raman and photoluminescence spectrophotometry. Furthermore, the existence of built-in potential and photo-switching behavior is demonstrated between the strained and unstrained region, constructing a self-powered homojunction photodetector. This approach provides a simple strategy to couple strain effect and plasmonic effect, which can provide a new strategy for designing high-performance and broadband 2D optoelectronic devices.