Study the structure of carbon nanotube cathodes with high emission current

More and more attention has been paid to carbon nanotubes (CNTs) for their remarkable electronic and mechanical properties. Besides application in flat panel display, CNTs have potential application in microwave power amplifiers for their good electron field emission properties. To be used as a cold cathode source for a microwave power amplifier, CNTs cathode should have high current as well as high current density. Due to the influence of the fringe field, the emission characteristic of the CNTs near the edge of the emission area is larger than that in the center. In this paper, we used a diode structure with square CNTs film. We computed the electric field of the diode model by finite difference method, then estimated the emission current density of the cathode and got the whole emission current by integral method. To make use of the fringe field, we divided the CNTs film into several elements. From the calculation results, the total emission current could be improved by optimization.