Enhancing the Ultraviolet Photocurrent and Response Speed of Zinc Oxide Nanoflowers using Surface Plasmons of Gold Nanoparticles and a Graphene Membrane

The enhancement effect of the plasmonic resonance of AuNPs and a graphene membrane on the optoelectronic properties of ZnO nanoflowers is investigated. A layered structure is fabricated, consisting of ZnO nanoflowers grown on a conductive fluorine-doped tin oxide (FTO) glass substrate, decorated with gold nanoparticles, and covered by a multilayer graphene membrane. An excellent photocurrent response as high as 1650 A W-1 and a millisecond level response time are achieved. Compared with the pristine ZnO device, which has a responsivity of 2.98 A W-1 and a response time of tens of seconds, the photocurrent response is dramatically increased by 500-fold and the response time is decreased by over 1000-fold. The significant enhancement of the photocurrent can be attributed to the coupling of plasmonic resonance modes of AuNPs and the graphene membrane, according to finite-difference time-domain simulation results; whereas the tremendous improvement on response time can be attributed to the high electron mobility of graphene. The work is essential for further study of the plasmonic enhancement of ZnO optoelectronic performance and provides a new path for the fabrication of ZnO-based high-responsivity, high-speed, and low-cost ultraviolet emission and detection devices.