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.
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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.
KOOL, and very important (once upon a time, a long time ago, I designed some vacuum tube based aps.).
I worked navigation radar in the USAF in the 80s and early 90’s and we didn’t replace all our old tube sets until right before I left the field for other endeavors. The first troubleshooting step was always to take the covers off, flip off the lights and look for the nonglowing tube. Worked about 90% of the time. Then the hard part came…removing the tube without touching one of the high voltage capacitor arrays. They bite!!! (The technical manual said to discharge them first, but that was for wimps.)
Even my ground radar contemporaries had solid state up to the final power stage, then most of them had some combination of travelling wave tubes for the final power output stage.
For the high GHz devices we always had trouble because all the solid state stuff was very exotic and expensive and the first thing we did in any receiver was knock the frequency down to a reasonable intermediate frequency that didn’t get into the nonlinear range of the transistors since sometimes the return frequency offset was the important bit of information we were trying to process. In the process we lost some phase information that could have been used to improve resolution. If you have receiver parts that can operate at the received RF, you don’t lose anything in translation, and might be able to do some pretty nifty phase and edge comparisons to separate closely spaced targets or even get single or few pulse imaging techniques. It could open up many things.
The missile I repaired in the Army, the Hawk Misslie had one transistor and boat loads of electron tubes, mostly 5703, 5704 and 5707s. The radars were basically all electron tubes too, they used a 4CX1000 as a voltage regulator!
Well, george, with the speed of light being about 1 ns per foot (1 x 10^-9 ns/foot), the propagation delay time for a typical ‘gate’ implemented in the following device technologies results in these propagation delay times:
a) ECL = 2ns
b) TTL = 1.5 – 33ns depending on type: conventional TTL ~ 9ns, Advanced Schottky ~1.5ns
c) RTL = 25ns
d) CMOS = 5 – 20ns depending on type: conventional CMOS, TTL pin compatible CMOS, high speed TPC CMOS or TTL compatible CMOS
So, we still have various ‘delays’ far exceeding a foot’s worth of wiring in most ‘gates’ (whose dimension we will stipulate is on the order of half an inch). Now, a gate is comprised of between 1 and 5 internal stages, with CMOS being probably the simplest for an inverter ‘gate’ at 1 stage. Fewer internal stages with faster switching time transistor reduces the overall ‘delay propagation time’ in a ‘gate’ then.
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Some of these old valves were veritable works of art – true sculptures. My brother still uses an old valve wireless.
Tsk Tsk says;
“Similarly, tubes are intrinsically rad hard compared to any semiconductor.”
Yes, BUT, you need to consider the VOLUME, yes they are more intrinsically rad hard, but they are BIGGER, so I can stuff more stuff that is less RAD HARD in a smaller “shielded can” and still get the same performance out of the system. This is what’s called a “trade study” in the industry, do I use a radiation hard device with no shielding, or do I use a “less” radiation hard device with some shielding ??? This is why you can make big bucks in the aerospace industry.
Boy, I never thought I could start a “RADIATION HARDNESS” debate on the “WUWT” website, I work with a Senior IEEE Fellow that has DEDICATED 30 plus years of his career to this topic, I consult him when I need advice on what SHOULD work out there in space. A whole bunch of those satellite images that are enjoyed by us have all been been produced by systems that he helped certify as “space ready”.
Man, I bet I could talk to 1,000,000 folks on the street and I could not find more than one who even knows what the heck “radiation hardness” even means……….
Cheers, Kevin
Once upon a time far away it was interesting to listen to the SW overseas broadcasts from the UK and the USA. We would sit many evenings in a darkened room intently listening to the radio as it faded in and out. The radio tubes would glow in the dark like little coals in the fire place and provide some warmth. The tubes seemed magical in that they could bring news from far away. Winston Churchill and Harry Truman would give encouraging speeches.
My favorite tube was the EF50 but when transistors came along vacuum tubes were supplanted by solid state devices for small signal applications.
Vacuum tubes still dominate at high power. The best way to provide 50 kW CW at 178 MHz for a 1 GeV storage ring (Duke University Free Electron Laser, 1995) was the 4CX100000 tetrode. When an upgrade to 200 kW RF output was needed (2005), larger tetrodes made in Russia were the obvious choice.
Klystrons vacuum tubes with over 50 MW of pulsed RF output are available for L-band (~1.5 GHz), S-band (~2.8 Ghz) and X-band (~11 GHz). You can even get 2 MW CW at 350 MHz.
When it comes to fast switching, the krytron (radio-active cold cathode) is the best option when you need a few Mega-Watts with sub-nanosecond jitter times. While my work had nothing to do with weapons technology it was really difficult to get supplies of these devices owing to their applications in Plutonium based weapons.
It looks as if vacuum tube technology will have application in small signal high bandwidth devices, once again. Now what did I do with my lecture notes from A.H.W. Beck’s classes?
Mike Bromley the Canucklehead says:
May 24, 2012 at 6:04 pm
“I enjoy the plasma burst from the quartet of 6L6′s in my Fender Twin Reverb…as I flip the standby switch. The smell of phenol in the evening…..mmmmmmmm! Moments later, the fuzzing and fritzing of the preamp-stage 12AX7′s, slightly microphonic. Yep!”
“Right on! I have solid state Pevey’s and Marshall’s, and nothing screams like my ’64 Fender Super Reverb. And no complement is more satisfying than have someone aproach and say, “What the hell have you got there.” Yes – there are somethings that can’t be replaced, at least on earth.
As an AGW skeptic who happened to make and sell tungsten light bulb based vacuum-tube-look “Tube Lamps” in danger of being banned I had to be careful not to be biased indeed but extra motivation was certainly there to get the word out, online. The way the eye works, exposed filaments that glow like vacuum tubes cause psychological pain due to glare, in that the eye cannot adjust the iris down to protect it from the glare. So! I learned to stick with designs that placed several exposed bulbs next to each other, providing a large enough area on the retina for the eye to get the message that it was O.K. to close the iris a bit since there was enough light to still see the room safely. My WWII veteran father who repaired aircraft instruments in Alaska used to try to teach me vacuum tube physics on paper in the era of the transistor. The take home message was that the inner design of the tubes themselves involved mostly hocus pocus! The physics was the simple part.
Yabut, can you test them in a drug store?
Mike Bromley the Canucklehead says:
Paul Marko says:
Exactly- My Mesa Boogie sounds better than any solid state on the market. 2x12AX7 pre-amps RULE!
Does this mean the Met Office will be able to work out how much hotter it’s going to get faster than they do now?
James Bull
“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.”
High frequency?!?!?! Tesla would approve.
Great, maybe we can get back to some real wah! Digital guitar amplifiers can do some neat stuff, but the wah wah is pathetic.
Nano vacuum tubes could be useful in digital x-ray cameras where radiation damage is a problem.
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Marian says:
May 24, 2012 at 5:03 pm
Cool.
That’ll open up more radio spectrum. When do we get to use 460GHz ham band? 🙂 “””””
Why would you want to waste your time Hammimng in those “dc” bands below 460 GHz. A ham former colleague of mine already recorded a communication with another ham on some field day exercise, back around 1990, at a carrier frequency of about 458 THz; and I myself demonstrated voice and music transmission over exactly the same frequency, back in 1967. My transmission was quite low tech; all done inside the lab to show I had nothing up my sleeve; but the 1990 exercise was quite high tech, and employed a silicon CMOS receiver chip, that I designed. The CMOS chip itself was quite small, only 500 x 600 microns; most of which, was the three connection pads. (but still a very primitive 800 nm technology, compared to today’s 22 nm chips). That transmission was across the whole of SF Bay, and that was far from max range at 458 THz.
The transmitter chip was actually an off the shelf transmitter. Today, you can get over 700 THz chips.
And as distinct from the Gore/Hanson CO2 propaganda, vacuum tubes really were susceptible to feedback initiated “tipping points”. Maybe we should be careful before we go too far down this track?
There’s a lunatic fringe of so-called hi-fi nutz, who still believe that valve amplifiers sound better than transistor ones; the sound is “warmer” they claim. Well I never ever heard, a “warm” symphony orchestra, and the 4-manual pipe organ I used to play in Palo Alto never was warm. I know valve amplifiers can be warm; I burned my nuckles many times, on those 807s in my early Williamson Amplifiers. The distortion in even the best speakers, is orders of magnitude higher, than a well designed solid state hi-fi amp; so there’s no way a valve amp could be lower in distortion or noise. Yes they sound different; it’s called “hiss” and is much like tonitis. You can go into Fry’s and watch all the yuppies going gaga over some “matchbox Bose” system; but how do you tell if it sounds good if all they play on it is that Canadian shrieker; no offense to Canadians; but I would much rather listen to the amplified sounds of a fine Swiss mechanical watch with sand in the gears.
Not a new idea. 30 years’ ago I was developing nano-engineered cold cathodes ad went to a field emission conference in Paris.
The technology lives on as cold cathodes in the miniature florescent lamps.
Nice! But as another old-timer who remembers firebottles fondly (including most of the type numbers mentioned here!), I’m holding out for a glass top on the chip, so that when you overload the thing you can see the pretty purple plasma light show!
The biggest “bottles” I ever had I donated to the UK’s National Valve Museum. Look ’em up – type MZ2-200. Hand-built beauty from another age.
The death of the vacuum tube described in the article in the 1960s is premature. In 1980 I still had callouses on the pads of my right thumb, forefinger, and middle finger from pulling hot vacuum tubes out of television sets. Transistorized televisions (except the CRT of course) didn’t go on the market until the early 1970’s and vacuum tube models were still be manufactured in the middle 1970’s. Typical service life of a television from that period was 15-20 years. The picture tube would be pretty faded by that time and you’d almost certainly have few tubes replaced and the mechanical contacts on the channel changer cleaned with a solvent once or twice but otherwise they were built like tanks. Vacuum tubes persisted in the form of picture tubes to probably the year 2000. My last set with a picture tube died this year – a 35″ Sony that was about 14 years old. It was actually still working but I got a new larger flat screen and gave away the 200 pound dinosaur and it didn’t survive the trip in the back of a pickup truck to its new home.
gallopingcamel says:
May 24, 2012 at 9:01 pm
Vacuum tubes still dominate at high power. The best way to provide 50 kW CW at 178 MHz for a 1 GeV storage ring (Duke University Free Electron Laser, 1995) was the 4CX100000 tetrode. When an upgrade to 200 kW RF output was needed (2005), larger tetrodes made in Russia were the obvious choice.
Klystrons vacuum tubes with over 50 MW of pulsed RF output are available for L-band (~1.5 GHz), S-band (~2.8 Ghz) and X-band (~11 GHz). You can even get 2 MW CW at 350 MHz.
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I was a weather- radar technician in the mid-1970s. As I recall the unit I was qualified on used a klystron for the local oscillator and a magnetron for the final stage.
Ask any electric guitar player: valve (tube) amplifiers just sound better. That’s why they never did go quite the way of the dinosaurs – there remained a small group of dedicated trolls living in caves who have, these past forty years, been hand-carving valves out of granite for the benefit of us old rock ‘n’ rollers. Marshall, Orange – I’m a Laney man myself – still make proper amplifiers.