Field emission characteristics of ZnO nanotetrapods and the effect of thermal annealing in hydrogen

Large-scale tetrapod-like ZnO nanostructures have been synthesized using a thermal chemical vapor deposition method on a silicon substrate. The high-purity nanotetrapods show sharp tips geometry with a wurtzite structure. The field emission properties of the uniform ZnO nanostructural material are investigated at different anode-cathode distances. The turn-on field for the ZnO nanotetrapods is found to be about 3.7 V/μm at a current density of 1 μA/cm2. The field emission behavior obeys Fowler-Nordheim relationship. More importantly,the field emission properties are improved after an-nealing in hydrogen,and therefore high emission current and low turn-on field are obtained. These results indicate that tetrapod-like ZnO nanostructures are a promising candidate for cold cathode emitters.