Coplanar nanoscale vacuum electron field emission triode with controllable gate distance

The typical nanoscale vacuum field emission triode with a controllable gate distance, created via focused ion beam etching and photolithography, is presented in this study. The field emission performance under coplanar gate control is distinguished from the gate distance (d_g) in a low vacuum environment. It is, therefore, necessary to highlight a vital parameter d_g defined by the nanogap between the center of the nanoscale channel and the edge of the coplanar gate, to methodically illustrate the working mechanism. For the case of a device with large d_g, the F-N tunneling current was positively increased by up to one order of magnitude when high bias conditions on the anode and coplanar gate were applied. In contrast, the device with short d_g displayed a negative drop in F-N tunneling current under the same measurement condition. As the gate bias increased continuously to a critical value, this device became cut off in this situation with an insignificant gate leakage current. This opposite trend of F-N emission current is eventually verified to have a relationship with d_g and it is suggested to play a crucial role in the device. This work clarified the role of the coplanar gate when device operated in the F-N tunneling mechanism and conducted a thorough analysis of the charge transport mechanism related to d_g. This work will aid coplanar nanoscale vacuum electron field emission device design in the future.