Negative photoconductivity of WS2 nanosheets decorated with Au nanoparticles via electron-beam irradiation

Tungsten disulfide (WS2) nanosheets (NSs) decorated with Au nanoparticles (NPs) were synthesized, and the effect on the WS2 NS photoresponse was investigated. The WS2 NS-decorated Au NPs showed a 2470% enhanced photoresponsivity compared with the WS2 NSs without Au NP decoration. The Au NP decoration resulted in the change from positive to negative photoconductivity (NPC) under 450-nm laser illumination. Compared with those without Au NP decoration, the WS2 NS-decorated Au NPs showed longer rising and falling times. The origin of the enhanced photoresponse and NPC were investigated. Finite-difference time-domain calculation was conducted. An electron-trapping-based NPC mechanism was proposed.