Miniature on-chip vacuum tubes could power efficient wireless communication devices.

Though superseded for most applications by the solid-state transistor, the venerable vacuum tube boasts one big advantage over its younger usurper: power. Free of stuff between its electrodes, a vacuum tube can operate at currents that would ohmically toast a transistor's semi-conducting innards. Vacuum tubes remain the technology of choice for high-power amplifiers, magnetrons, and klystrons.

Now, a team led by Wei Zhu of Agere Systems in Murray Hill, New Jersey, has built a device that could propel the vacuum tube out of its traditional niches.(n1) The Agere device, a 100-µm-scale triode, exploits two of the hottest technologies of the past decade: carbon nanotubes and micro-electromechanical systems (MEMS). And because the new triode sits on a silicon substrate, it could readily plug into an integrated circuit. Agere developed the triode as a proof of concept. Devices like it could end up in compact wireless transmitters.