Hybrid single/poly-crystalline ZnO nanoawl arrays: facile synthesis and enhanced field emission properties

Arrays of hybrid single/poly-crystalline ZnO nanoawls (HSP-ZNAs) composed of single-crystalline ZnO nanorod (ZNR) holders and poly-crystalline nanoneedles were for the first time fabricated via a facile two-step synthesis strategy that was based on firstly an aqueous electrodeposition and secondly an aqueous chemical growth (ACG). The two-step synthesis strategy not only can ensure reliable electrical contact between the ZNR holders and the substrates, but also can afford control over the crystal structure and aspect ratio of the nanoneedles. The as-grown HSP-ZNA arrays exhibited markedly enhanced field emission (FE) current at lower electric fields compared with the whole single-crystalline ZNA arrays or ZNR arrays without nanoneedles. The improvement could be attributed to more emission sites from the tips of poly-crystalline nanoneedles of the HSP-ZNAs. Our results demonstrate the HSP-ZNA arrays one of the promising candidates for FE devices, and also provide a new paradigm for synthesizing novel hybrid single/poly-crystalline nanostructures that could find many potential applications in electronics and optoelectronics.