Enhanced field emission of ZnO nanowire arrays by the control of their structures

Four kinds of ZnO nanostructrues, i.e. nanorods, nanopencils, nanotowers, and nanoneedles, were successfully synthesized by chemical vapor deposition method, and their field emission properties were comparatively investigated. The results showed that field emission performance was strongly affected by nanowire morphology, and the nanotower-like ZnO exhibited the lowest turn-on field of 4.36 V/μm. The classical F-N theory was employed to analyze the enhancement mechanism. It was found that only the optimized combination of field enhancement factors and geometrical factors could assure excellent field emission performance.