Zinc oxide nanowire based field emitters

We report the field emission properties of 50 nm diameter ZnO nanowires that were electrochemically self-assembled within pores of an anodic alumina film. Current versus voltage measurements of the Fowler–Nordheim tunneling current indicate that the turn-on field is 15 V μm−1 and the field enhancement factor β calculated for two sets of samples turned out to be 670 and 1481, respectively (theoretical value for β in bulk ZnO is 205). The enhancement in β is most likely due to the large aspect ratio of the nanowires. Variation in the length of the nanowires causes the screening effect, which increases the turn-on field and reduces the emission current density. The current–voltage characteristics of the wires are non-linear and show a rectifying behavior.