Emission efficiency dependence on the tilted angle of nanogaps in surface conduction electron-emitter

In this work, the emission efficiency of the novel surface conduction electron-emitter corresponding to tilted angles (thetas) of the driving electrode is studied numerically. Due to the small angle, the emitter apex becomes significant and induces large electric field. The large electric field then attracts more particles into vacuum and then increases the emission current. However, the structure of the driving electrode limits the electron trajectory while the angle decreases, and it reflects the portion of collected current by the anode decreases and makes a drop in emission efficiency. It shows there is the highest emission efficiency (about 37%) under an optimum angle thetas = 60deg. The result provides an insight into the relation between emission efficiency and emitter apex.