Different morphologies of comb-like ZnO and oriented ZnO nano-arrays such as ZnO nanoneedles and ZnO nanorods were synthesized by using flexible thermal evaporation method via simply adjusting the temperature and oxygen content.The ZnO nanorods arrays have the lowest turn-on field,highest current density and the largest emission efficiency owning to its good contact with the substrate and relatively weaker field screening effects. The experiments show that the morphologies and orientation of one-dimensional(1D) ZnO nanomaterials have considerable effects on the turn-on field and the emission current density,and the nanoarray also contributes to electrons emission.The results could be valuable for the application of ZnO nanorod arrays as cathode materials in field emission based devices.
Carbon nanotube(CNT) cathodes prepared by electrophoretic deposition were treated by a combination of nickel electroplating and cathode corrosion technologies.The characteristics of the samples were measured by scanning electron microscopy,energy dispersive X-ray spectroscopy,J-E and F-N plots.After the treatment,the CNT cathodes showed improved field emission properties such as turn-on field,threshold electric field,current density,stability and luminescence uniformity.Concretely,the turn-on field decreased from 0.95 to 0.45 V/μm at an emission current density of 1 mA/cm^2,and the threshold electric field decreased from 0.99 to 0.46 V/μm at a current density of 3 mA/cm^2.The maximum current density was up to 7 mA/cm2 at a field of 0.48 V/μm.In addition,the current density of the CNT cathodes fluctuated at around 0.7 mA/cm^2 for 20 h,with an initial current density 0.75 mA/cm^2.The improvement in field emission properties was found to be due to the exposure of more CNT tips,the wider gaps among the CNTs and the infiltration of nickel particles.
