A micromachined vacuum triode using a carbon nanotube cold cathode

A fully integrated on-chip vacuum microtriode using carbon nanotubes as field emitters was constructed laterally on a silicon surface using microelectromechanical systems (MEMS) design and fabrication principles. Each electrode in the triode was made of a hinged polycrystalline silicon panel that could be rotated and locked into an upright position. The device was operated at a current density as high as 16 A/cm². Although the transconductance was measured only at 1.3 μS, the dc output power delivered at the anode was almost 40 × more than the power lost at the grid electrode. The technique combines high-performance nano-materials with mature solid-state fabrication technology to produce miniaturized power-amplifying vacuum devices in an on-chip form, which could potentially offer a route of integrating vacuum and solid-state electronics and open up new applications for "old-fashioned" vacuum tubes.