Oscillating current observed in field emission from a single zinc oxide nanostructure and the physical mechanism

A phenomenon of field emission instability is reported. Field emission current oscillation was observed when a single zinc oxide (ZnO) one dimensional nanostructure operated at high current density. As a result, the radius curvature of the nanoemitter apex was sharpened to less than 15 nm. This indicates the oscillation was associated with melting of the emitter material. We found that the oscillation may be ascribed to (i) the behavior of charging and (ii) the shape changing of a metallic liquid ball that exists at the tip apex under high electric field. The net force of electric force and surface tension modifies the radius of the apex periodically, which results in the oscillation of field emission current. This finding may enhance the understanding of the physical process of field emission from ZnO nanostructures.