A novel micro-machined mesh grid for a triode-type carbon nanotube field emitter

An efficient electron source is developed by using a micro-machined mesh grid having opening ratio of 67% as an extraction gate for a triode-type field emitter, the cathode of which is a film of vertically-aligned carbon nanotubes (VACNTs) that are synthesized by a hot-filament chemical-vapor-deposition process. The threshold electric field defined for the cathode current of 1 µA is about 0.27 V/µm. The cathode and the anode currents as large as 250 and 140 µA, respectively, are obtained at the electric-field strength of 0.44 V/µm. The electron transparency that corresponds to the ratio of the anode current and the cathode current is approximately 60% for anode currents larger than about 2 µA regardless of anode-bias voltage.