Plasmonic WS₂ Nanodiscs/Graphene van der Waals Heterostructure Photodetectors

Two-dimensional material van der Waals (vdW) heterostructures provide an excellent platform for design of novel optoelectronics. In this work, transition-metal dichalcogenide WS₂ nanodiscs (WS₂-NDs) of lateral dimension of 200-400 nm and layer number of 4-7 were synthesized on graphene using a layer-by-layer, transfer-free chemical vapor deposition. On this WS₂-NDs/graphene vdW heterostructures, localized surface plasmonic resonance (LSPR) was achieved, resulting in remarkably enhanced light absorption as compared to the counterpart devices with a continuous WS₂ layer (WS₂-CL/graphene). Remarkably, the photoresponsivity of 6.4 A/W on the WS₂-NDs/graphene photodetectors is seven times higher than that (0.91 A/W) of the WS₂-CL/graphene vdW heterostructures at an incident 550 nm light intensity of 10 μW/cm². Furthermore, the WS₂-NDs/graphene photodetectors exhibit higher sensitivity to lower lights. Under 550 nm light illumination of 3 μW/cm², which is beyond the sensitivity limit of the WS₂-CL/graphene photodetectors, high photoresponsivity of 8.05 A/W and detectivity of 2.8 × 10¹⁰ Jones are achieved at V_sd = 5 V. This result demonstrates that the LSPR WS₂-NDs/graphene vdW heterostructure is promising for scalable high-performance optoelectronics applications.