Regulator tube in operation (via archive photography)
Silicon is breathing new life into the old vacuum tube technology we thought was all but gone. Sure some high-end stereo and guitar amplifiers still use them but this new/old technology is aimed at being used in computers…..again (remember ENIAC?). Vacuum tubes were used to amplify an electrical signal which was pivotal in the development of RADAR, radio, television and even digital computers till the early fifties when the first silicon transistors came on the scene. They could do the same thing as the tubes (rectification, amplification and switching) except they were considerably smaller, cheaper, could be integrated into microchips and longevity dwarfed the tubes. The down side of using silicon transistors is that they’re slower than vacuum tubes (electrons have to move through a solid rather than a vacuum) and are extremely susceptible to radiation (wreaking havoc on the electron flow) which makes using the semiconductors in radiation-rich environments, such as space, a big problem for NASA and the military.
ENIAC, vacuum tube based computer system from 1946. Weighs 27 tonnes, holding 17,468 tube. (via archive photography)
To overcome those short-comings, a team of researchers from the NASA Ames Research Center and the National Nanofab Center in South Korea combined the two technologies into what they call the ‘nano-vacuum tube’. Led by Meyya Meyyappan (NASA), the team developed the tube by ‘etching a tiny cavity in phosphorus-doped (for modulation of the semiconductors electrical properties) silicon’. The cavity is then bordered by three electrodes that form the gate, source and drain which is separated by only 150 nano-meters. The team designed a very tiny vacuum tube that doesn’t need to rely on a vacuum as the electrons have an extremely short distance to travel and, therefore, will not run into any stray atoms along the way. The team found that their new nano-vacuum tubes ran considerably faster (estimated at 0.46 terahertz) at higher voltages (10 volts) over their current silicon cousins, however implementation is still far off as the development of the nano-vacuum tube was primarily a ‘proof of concept’ experiment and compatible technology doesn’t exist yet for their use.