From AAAS, news of a super tiny vacuum-tube transistor hybrid that can operate up to .46 TERAHertz (thats 460,000 megahertz or 460 gigahertz):
Return of the Vacuum Tube
by Jon Cartwright
Peer inside an antique radio and you’ll find what look like small light bulbs. They’re actually vacuum tubes—the predecessors of the silicon transistor. Vacuum tubes went the way of the dinosaurs in the 1960s, but researchers have now brought them back to life, creating a nano-sized version that’s faster and hardier than the transistor. It’s even able to survive the harsh radiation of outer space.
Developed early last century, vacuum tubes offered the first easy way to amplify electric signals. Like light bulbs, they are glass bulbs containing a heated filament. But above the filament are two additional electrodes: a metal grid and, at the top of the bulb, a positively charged plate. The heated filament emits a steady flow of electrons, which are attracted to the plate’s positive charge. The rate of electron flow can be controlled by the charge on the intervening grid, which means a small electric signal applied to the grid—say, the tiny output of a gramophone—is reproduced in the much stronger electron flow from filament to plate. As a result, the signal is amplified and can be sent to a loudspeaker.
Vacuum tubes suffered a slow death during the 1950s and ’60s thanks to the invention of the transistor—specifically, the ability to mass-produce transistors by chemically engraving, or etching, pieces of silicon. Transistors were smaller, cheaper, and longer lasting. They could also be packed into microchips to switch on and off according to different, complex inputs, paving the way for smaller, more powerful computers.
But transistors weren’t better in all respects. Electrons move more slowly in a solid than in a vacuum, which means transistors are generally slower than vacuum tubes; as a result, computing isn’t as quick as it could be. What’s more, semiconductors are susceptible to strong radiation, which can disrupt the atomic structure of the silicon such that the charges no longer move properly. That’s a big problem for the military and NASA, which need their technology to work in radiation-harsh environments such as outer space.
…
The new device is a cross between today’s transistors and the vacuum tubes of yesteryear. It’s small and easily manufactured, but also fast and radiation-proof. Meyyappan, who co-developed the “nano vacuum tube,” says it is created by etching a tiny cavity in phosphorous-doped silicon. The cavity is bordered by three electrodes: a source, a gate, and a drain. The source and drain are separated by just 150 nanometers, while the gate sits on top. Electrons are emitted from the source thanks to a voltage applied across it and the drain, while the gate controls the electron flow across the cavity. In their paper published online today in Applied Physics Letters,
Full story here at AAAS, here’s my concept pictorial image (may not be fully accurate – I don’t have access to their paper diagrams) of what it looks like compared to the traditional vacuum tube (triode) based on what I’ve been able to find on the design:
The paper from AIP:
Vacuum nanoelectronics: Back to the future?—Gate insulated nanoscale vacuum channel transistor
Jin-Woo Han1, Jae Sub Oh2, and M. Meyyappan1
1Center for Nanotechnology, NASA Ames Research Center, Moffett Field, California 94035, USA
2National Nanofab Center, 335 Gwahangno, Yuseong-gu, Daejeon 305-806, Korea
(Received 24 February 2012; accepted 22 April 2012; published online 23 May 2012)
- A gate-insulated vacuum channel transistor was fabricated using standard silicon semiconductor processing. Advantages of the vacuum tube and transistor are combined here by nanofabrication. A photoresist ashing technique enabled the nanogap separation of the emitter and the collector, thus allowing operation at less than 10 V. A cut-off frequency fT of 0.46 THz has been obtained. The nanoscale vacuum tubes can provide high frequency/power output while satisfying the metrics of lightness, cost, lifetime, and stability at harsh conditions, and the operation voltage can be decreased comparable to the modern semiconductor devices.
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Wow, very interesting. AS I recall, those old tubes were resistant to EMP damage as well.
Very interesting how we can make old stuff better rather than just replacing it.
I remember my old valve amp very well. I suspect my neighbors at the time still do too, and they lived about 500m away!
Hmmm I wonder how this will play out regarding maximum data rates for digital systems?
That is a huge achievement!
Larry
Way cool!
Vacuum Tubes have always been superior to transistors at RF.
Check any TV or Radio station transmitter.
Tubes were naturally suited to analog uses because of their response curve. I wonder if this technology will finally make super-complex analog computers … i.e. true neural equivalents … more feasible?
EMP resistive, Gama resistive, and need little shielding in space..
great achievement… and one that will push out telecommunications abilities to great lengths by reducing weight needed in space for them to operate…
460GHz, amazing, Bye-Bye travelling wave tubes. Not sure the diagram is quite accurate. Of course, first you need a vacuum and are able to keep it.
As an avid ham radio operator – I collect 1950’s era tube transmitters and receivers. I have always loved the warm glow of vacuum tubes. I use a transceiver that has 3 vacuum tubes in it daily. Tubes are able to take abuse that solid state devices cannot – plus they have made a huge ‘comeback’ with audiophiles because they have a much better ‘sound’. Don’t get me wrong, I deal with digital devices on a daily basis & they are indeed wonderful, but if you want a device that can literally take some serious abuse and ‘keep on ticking’ – vacuum tubes win every time. Great stuff!
BTW I remember meddling with my valve radios and amplifiers.
BBTW There is a company in the UK named E2V which makes blazingly fast (and yes, they are also hot) analog-to-digital converters. They used to be The English Electric Valve Company. (Ed Note: The Brits call a vacuum tube a “valve”).
KT66 anyone?
At the first glance, this appears to be a solution looking for a problem. The speed of integrated circuits is determined mostly by delays in “wires”, not by delays in individual transistors.It could become important in true 3-dimensional circuits; the vacuum should generate much less heat.
12AU6s are OK, but you can’t beat an output stage of glowing KT88s.
This reminds me of a 1951 sci fi short story which included a future space fleet battle computer with “a million vacuum tubes”:
http://www.mayofamily.com/RLM/txt_Clarke_Superiority.html
Reading it decades later in the era of transistors and laptop computers, I smiled indulgently at the author’s lack of vision.
Oh, wait…
I think the structure may be more like a vacuum between source and drain and the metal gate physially on top of the vacuum space between the two, insulated by SO2.
The concept is not new, the basic idea was being bandied around physics depts here as early as the late 1960’s. The essential problems are current density, low, dissipation of waste heat, and of course engineering the blighters to close enough tolerances.to operate. I forget the order of voltage gradient you need for what were then called cold cathode valves, and I am not going to look up my notes, but I seem to remember it is really rather high which causes other engineering problems.
But of course the truth is at that time the transistor had become incredibly cheap, the integrated circuit was starting to appear and nobody was much interested. There was a revival in the mid eighties with much better field computation techniques but nothing came of it, the engineering was still too difficult.
Time will tell whether these new fabrication techniques work well enough to produce a commercially viable product.
Still I have a certain nostalgia for glass bottles with fires in, UK and US designations were not the same, but my particular favourite was the mighty KT 66.
Kindest Regards
A NEW TOY! YAAAAAAAAY!
I suspect it will be a few years, but I look forward to seeing them in action.
One wonders if they will be able to replicate the more subjective differences in things like Amp output frequencies that cause people to keep building tube amps, and if they will actually be EMP-hard or if that is too dependent on everything *else* in a circuit.
I just never know what to expect on WUWT. It will surely be the cutting edge of science and/or technology.
Thanks Anthony.
A little background (and more info) on “Vacuum Transistors”, as they have been tried before (processing technology has advanced a lot since then, however, perhaps making this practical now):
http://tikalon.com/blog/blog.php?article=2012/vacuum_transistor
.
Cool.
That’ll open up more radio spectrum. When do we get to use 460GHz ham band? 🙂
Bill Marsh says:
May 24, 2012 at 4:04 pm
Which made the Soviet systems much more survivable than US systems since they had mostly vacuum tube systems long after we had switched to transistors. Audiophiles that I knew also prized “Red” tubes since they had really refined their manufacturing techniques.
I like these small atomic clocks too:
http://www.symmetricom.com/products/frequency-references/chip-scale-atomic-clock-csac/SA.45s-CSAC/
Marian says:
Cool.
No. Hot 😉
Not so much anymore; all your AMs are now solid state (saves TONS on cost of electricity), and everything except the PA stage in your UHF TV transmitters are tube/thermionic-emission devices …
As an example, take a look at the AM broadcast transmitters in the 3DX Transmitter Family from Harris, all solid-state with output power levels of 25, 50 and 100 kW (Kilowatts) and HD (digital) capable out of the ‘box’:
Overview – http://www.broadcast.harris.com/media/3DXTransmitterFamily_25-20445.pdf
Datasheet – http://www.broadcast.harris.com/media/3DXAMTransmitterFamily_25-20959.pdf
Note that overall “AC” (input power conversion to RF) efficiencies are better than 85%.
.
Neat!
BTW, valve audio amps are still being produced in the UK: http://www.fat-man.co.uk
Operation up to 460 GHz is mind boggling, but there will be the same (or greater) power limitations as with all solid state devices. They are only around 50 % efficient, so a lot of heat has to be conducted away with heat sinks. High power devices are therefore impractical. I use a homebrew pair of 4-400s for a KW PEP out on 3.8 MHz and some other bands. I use a pair of 3CX800A7’s for legal 1500 watts out on 144 MHz and 432 MHz. Tubes are a little more efficient, ~ 65%, and not going to be replaced any time soon for high power applications. With low power, even 5 watts, you can be heard all over the world. With high power you can do things that you can not do with low power- like hear your echoes off the moon! There is very little ham radio operation above 10 GHZ. With the described device we can, I suspect, investigate the frequency spectrum 142-149 GHz, 241- 250 GHz, and everything above 300 GHz, all of which has been allocated by the FCC to ham radio. We pioneered the exploration and use of much lower frequencies in the 20th century. Maybe we can again!