2.2: Field emission behavior of ZnO nanowire planar cathodes

Zinc oxide (ZnO) nanowires were deposited on a plane conductive surface. They were vertically aligned, with 3 μ and 140 nm respectively for the length and the diameter, and with an array density of 10 nanowires/μm². A field emission study by scanning anode field emission microscopy was performed to evaluate the field emission properties. The effective work function is about 1 eV, the threshold of the macroscopic field F_app is about 6 V/μm for a current density J_FE equal to 0.05 A/m², which is a rather low field. For J_FE greater than 500 A/m², the nanowires evolved into a bulbous apex by surface diffusion.