Carbon Nanotube Field Emission Devices with Integrated Gate for High Current Applications

We present a fabrication technique for the integration of a gate electrode with an array of carbon nanotube (CNT) emitters. These gated cathode structures have high emission current density and may be utilized in X-ray tubes, traveling wave tubes, and ion propulsion systems. The CNT emitters are grown directly on polished bulk metal substrates and are comprised of CNT bundles that are vertically aligned and can be uniformly produced over a large substrate area. These arrays present many advantages including the capacity to sustain current densities greater than 60 mA/cm² and turn-on fields as low as 0.9 V/mum. We also present a detailed integration scheme utilizing these arrays of CNT emitters for the fabrication of gated cathode structures. Relative to other CNT emitters these gated structures have low operating voltages at higher emission current densities. Finite element analysis is used to investigate the electrostatic properties of both gated and ungated pillar structures. These results demonstrate that the benefits afforded by CPAs can be further enhanced by the addition of an integrated gate electrode.