Graphene/WS2Nanodisk Van der Waals Heterostructures on Plasmonic Ag Nanoparticle-Embedded Silica Metafilms for High-Performance Photodetectors

Abstract

Coupling plasmons and excitons provide a promising approach to enhance the performance of photodetectors based on two-dimensional (2D) atomic layer heterostructures. Herein, we report a nanohybrid photodetector achieved by transferring a nonmetallic plasmonic WS2 nanodisk/graphene van der Waal (vdW) heterostructure grown using chemical vapor deposition, on metallic plasmonic Ag nanoparticles embedded in 20 nm thick silica (AgNP-metafilm) fabricated using in situ Ag and Si evaporation through a shadow mask. This nanohybrid photodetector enables not only superposition of the plasmonic effects from the two plasmonic nanostructures, but also the effective coupling of the plasmons and excitons in WS2 nanodisks upon illumination. This leads to a high responsivity of 11.7 A/W on the graphene/WS2 nanodisks/AgNP-metafilm under an incident illumination power of 5.5 × 10-8 W at 450 nm, which represents a 500% enhancement over that of the counterpart without the AgNP-metafilm. The finite element time-domain simulation of the local light field distribution indicates that the enhancement can be attributed to enhancement of exciton (electron-hole pair) excitation and exciton-plasmon coupling in the graphene/WS2 nanodisks/AgNP-metafilm photodetectors. In addition, the approach for fabrication of the graphene/WS2 nanodisks/AgNP-metafilm heterostructures is scalable and cost efficient and hence promising for commercial applications.