Stable field emission from ZnO nanowires grown on 3D graphene foam

Graphene was grown directly on nickel foam (NF) to form three dimensional graphene foam (GF), followed by growth of zinc oxide nanowires (ZNWs) on the surface of GF by a hydrothermal method. In comparison with pristine GF, the ZNW/GF hybrid structure exhibited efficient field emission with a low turn-on field of 1.7 V/μm, a low threshold field of 2.4 V/μm, high emission spot density, a high field enhancement factor of 1878 and excellent emitting stability. We proposed that the introduction of ZNWs on the surface of GF can increase the number of emission points, enhance tunneling probability, and lead to optimized field emission for the hybrid emitters. In addition, the graphene buffer layer provided a better electrical contact with ZNW, which also benefit to field emission.