Field Emission from a Composite of Graphene Sheets and ZnO Nanowires

There is a problem with field emission from graphene sheets (GSs) because existing deposition methods lead to sheets that have planar morphological features along entire substrates, which limits field enhancement. To overcome this problem, here we grow pyramid-like GSs on Ni-coated ZnO nanowires via a "base growth" mechanism using plasma-enhanced chemical vapor deposition. The surface morphologies of ZnO-GSs can be controlled by the density of the Ni nanoparticles and deposition time. The ZnO-GSs has a lower turn-on field, 1.3 V/mu m, compared to that, 2.5 V/mu m, of pure ZnO at a current density of 1 mu A/cm(2), implying avenues for potential applications of graphene and ZnO.