Interesting wikipedia article

[soundmasterg]

I read the wikipedia article on vacuum tubes and in the last paragraph, they talk about a possible new application for them. Thoughts anyone?

Greg

Vacuum tubes using field electron emittersIn the early years of the 21st century there has been renewed interest in vacuum tubes, this time with the electron emitter formed on a flat silicon substrate, as in integrated circuit technology. This subject is now called vacuum nanoelectronics. The most common design uses a cold cathode in the form of a large-area field electron source (for example a field emitter array). With these devices, electrons are field-emitted from a large number of closely spaced individual emission sites.

Their claimed advantages include greatly enhanced robustness combined with the ability to provide high power outputs at low power consumptions. Operating on the same principles as traditional tubes, prototype device cathodes have been fabricated in several different ways. Although a common approach is to use a field emitter array, one interesting idea is to etch electrodes to form hinged flaps – similar to the technology used to create the microscopic mirrors used in Digital Light Processing – that are stood upright by an electrostatic charge.

Such integrated microtubes may find application in microwave devices including mobile phones, for Bluetooth and Wi-Fi transmission, in radar and for satellite communication. Presently they are being studied for possible applications in field emission display technology, but significant production problems seem to exist.

[R.G.]

Yep. I remember first reading about these about 20 years ago. Sadly, it doesn't seem to have moved much. They would rapidly lead to ACO (Acronym Collision Overload) because the obvious acronym, "FET" for "Field Emission Triode" seems to have been taken. Perhaps that's why "vacuum nanoelectronics" was picked up.

The trick is to etch a silicon substrate with a number of resist dots in an array. The etch would make a number of columns in concept, but undercutting of the dots leads not to columns but to sharp-pointed "pins". The points concentrate electric field, and the points boil off electrons when the voltage between them and something else is big enough. The version I saw etched a forest of needles for some microns into the surface of a silicon surface, and then put two conductive rings around the pit. The first ring was the grid terminal, the second was the plate. The display specialized version used a separate plate held above the pit.

One screaming advantage is that, much like glass-bottle triodes, they're much more immune to radiation than other forms of electronics. It is conceivable that there is actually a thriving secret technology producing these for applications which the military wants to survive an EMP or a near nuclear strike. But that's purely speculation. It was a claimed advantage at the time I first read about them.

[R.G.]

Hey, this is even cooler than when I last saw it. See:

Diamond vacuum field emission devices

They're making field emission triodes on etched layers of diamond with low voltage operation and all the rest of the electrical engineering advantages of diamond.

[soundmasterg]

Thanks for posting that article R.G. Very interesting!!

Merlin posted this over at AX84 >> There is a professor at my university who works in this area. He developed a flat-screen television based on cold-cathode silicon triodes, but so far it is too expensive to be commercially viable. He has micrographs of things on the walls around his office!

And then he posted these two pages too about what this professor is doing apparently >> Nanostructures, Department of Electronics, University of York
http://www.elec.york.ac.uk/files/u12/NanoTipFig2.jpg

So it seems that someone is working on it somewhere....haha

Greg