Highly efficient field emission from large-scale and uniform monolayer graphene sheet supported on patterned ZnO nanorod arrays
A graphene/patterned ZnO (G/PZO) nanorod array composite was successfully fabricated by using the colloidal nanosphere monolayer templating strategy. Compared with graphene/compact ZnO (G/CZO) nanorod arrays, the G/PZO nanorod array composite exhibited a highly efficient and stable field emission with a low turn-on field. The field emission had a strong dependence on the density and the inter-distance of the emitters. By changing the diameter of polystyrene (PS) colloidal nanospheres, optimal emitter inter-distance was obtained. Graphene supported on ZnO nanorod arrays, patterned by an 886 nm PS colloidal nanosphere monolayer, displayed the best field emission with a turn-on electric field of only 6.4 V μm−1 and the field enhancement factor β was 1158. The K point in the Fowler–Nordheim plot demonstrated the electron tunneling mechanism took place in this composite material. The cyclic experiment showed that the field emission of the G/PZO nanorod array composite was of high stability.