Morphological effects on the field emission of ZnO nanorod arrays

The field-emission properties of ordered ZnO nanorod arrays with different morphologies were investigated in detail. After comparison of three different morphologies, it was found that the morphology of the ZnO nanorods has considerable effect on their field emission properties, especially the turn-on field and the emission current density. Among them, the ZnO nanoneedle arrays have the lowest turn-on field, highest current density, and the largest emission efficiency, which is ascribed to the small emitter radius on the nanoscale. On the other hand, high nanorod density remarkably reduces the local field at the emitters owing to the screening effect, which is related to the density of the emitters. The analysis results could be valuable for the application of field-emission-based devices using ZnO nanorod arrays as cathode materials. (c) 2005 American Institute of Physics.