Low-field electron emission from tetrapod-like ZnO nanostructures synthesized by rapid evaporation

Tetrapod-like zinc oxide (ZnO) nanostructures can be synthesized by rapid heating metal zinc pellet at 900 °C under air ambient. Catalyst, vacuum, and carrying gas are not necessary, and more importantly, it is a volcanic process for rapid and mass production. The turn-on field of the synthesized tetrapod-like ZnO nanostructures is found to be as low as 1.6 V/μm at the current density of 1 $\mu {\mathrm{A/cm}}^2.$ These ZnO nanostructures are technologically useful for vacuum electron devices because they can be easily and economically synthesized and deposited on large substrates.