Field emission from zinc oxide nanorod bundles grown on silicon nanoporous pillar array

A large-area zinc oxide (ZnO) nanorod bundle array was grown on a silicon nanoporous pillar array (Si-NPA) substrate by a chemical vapor deposition method, and its field-emission properties was studied. The structural characterization disclosed that the bundles were composed of hexagonal ZnO nanorods growing along c-axis and taking roots into the silicon pillars of Si-NPA. The average diameter and length of the ZnO nanorods were ∼145 nm and ∼10 μm, respectively. The field-emission measurements showed that the turn-on field of ZnO/Si-NPA was 4.6 V/μm with an emission current density (ECD) of 1 μA/cm2, and an ECD of 420 μA/cm2 was achieved at an applied field of 8.89 V/μm. The field enhancement factor was calculated to be ∼1700 based on the Fowler–Nordheim theory. According to the obtained charge coupled device (CCD) image, the density and brightness of the emission dots increased with the applied field, and the high emission dot density was attributed to the formation of a large number of ZnO nanorod emitting tips. Our results indicated that ZnO/Si-NPA might be a promising electron emission source.