Electron field emission through a very thin oxide layer

Field emission of an emitter covered with a very thin oxide layer is modeled and calculated numerically. The additional barrier due to the oxide layer is included in the tunneling problem by using the standard WKB method. The following physical parameters are considered: the oxide barrier height, the oxide conduction band-edge electron effective mass, and the oxide dielectric constant. Compared with the Fowler-Nordheim equation, which was derived for a clean metallic emitter, the calculation shows a reduction of the emission current density from an emitter covered with an oxide layer a few monolayers thick. After reaching a minimum emission current density, the emission increases when the thickness of the oxide layer increases further. Finally, the emission current density is saturated and stabilized