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.
My old high school electronics instructor was right. Transistors, and integrated circuits are just a fad after all, and having to construct a two tube superheterodyne AM receiver when every other high school kid in the country was playing around with op amps, and 555 timers, is now apparently going to pay off for me. Right?
George E. Smith, a very large portion of professional (studio grade) recording equipment still contains at least one vacuum tube. I’m sitting right beside both a microphone and a pre-amp that both have tubes, and they’re not old. There IS a warmer sound, and in truth there’s no good reason they couldn’t simulate the sound with solid state. The reality is the solid state guys get so obsessed with the accuracy of signal that they forget the vagaries of art.
One of the more popular plug-ins for digital recording software was the tube-sound.
The Abbey Road plug ins simulate the beautiful and highly inaccurate tube-driven compressors of the 60s.
Warmth is subjective. I can recognize it but I can’t describe it. My own voice through tube equipment (or a competent simulation) sounds better to my own ears than when it’s as accurate and precise as possible.
The standard “fuzz” effect for electric guitar will always be most pleasing when it’s an overdriven tube… and whether you like that sound or not (I know my parents hate it, like nails on a chalkboard to them), it’s a warmth that still hasn’t been accurately reproduced with solid state.
AJB says:
May 24, 2012 at 5:25 pm
Neat!
BTW, valve audio amps are still being produced in the UK.
What do you mean “in the UK?” They’re still being produced all over the world, and never went away. My most recent valve amp was Chinese, like everything else these days.
Steve in SC says: May 24, 2012 at 4:27 pm “Vacuum Tubes have always been superior to transistors at RF. Check any TV or Radio station transmitter.”
Too much of a sweeping statement. It depends what you want to do at RF. A fixed ground installation where you have plenty of space and lots of power available might favour electron tubes. However, a sophisticated mobile military air defence system with a phased array radar would be a different story.
Vacuum tubes didn’t “go the way of the dinosaur”; they continue to be used in applications where they are better than transistors, like high-power transmitters. Also transistors are definitely not “generally slower than vacuum tubes”, since transistors are generally much smaller (until now apparently) which makes them faster.
Steve in SC says:
May 24, 2012 at 4:27 pm
You are correct. In fact, a company in the Czech Republic is still making vacuum tubes used for superior sound reproduction. Here’s a How It’s Made rendition of that (mostly hand-made) process:
Wish I could afford a high-end system like that.
Way back when I was working in electronics I found signal to noise ratio from a front end valve amplifier much better than a transistorised front end. As far as the final audio amp is concerned, a transistor push-pull output was just as good as a valve, especially as you could power it with a car battery.
More than 50 years ago I used to design and build transmitters, receivers and amplifiers with vacuum tubes or valves. I bought my first transistor more than 50 years ago. My old homemade 1500W linear amplifier for 3.5 to 30 MHz uses a pair of 813,s operating at 3000 volts 0.5 ampere peak. I got my ham license in 1964…
Tempus fugit…
73
Agust, TF3 OM
How did this get published?
It doesn’t give the obligatory acknowledgement to the dangers of climatechange.
One minor correction. Transistors are slower than vacuum tubes of the same size. But since transistors could be made millions of times smaller than a vacuum tube, they ended up being faster. I’ll watch this development of micro-vacuum tubes with interest.
Another advantage to transistors was they used much less power and could operate at lower voltanges.
DirkH says:
May 24, 2012 at 6:40 pm
Actually…
Well it depends how you set up your computer. Digital computers use voltages to determine whether something is 1 or 0 and they tend to fall within ranges of the ideal on or off voltage state, so in that sense they’re not qualitatively dissimilar from a computer built from discrete analogue components, if that computer also operated in binary. The early computers were huge valve-built monstrosities and had no emergent properties.
However, part of the implication of “analogue computing” is the idea that it doesn’t operate in binary, using discrete voltage levels to determine on or off, but instead operates along a continuum of states. It would be difficult to impossible to replicate this using current digital hardware (though it could be simulated in any turing-complete device but, as anee fule kno, simulations are always missing something and any digital simulation of an analogue system would be quantised by its nature, thus introducing subtle “error” in how its components interact).
In analogue computing the emergence would likely come as a result of propagating waveforms within the circuits of the computer interacting in unpredictable ways. It’s been speculated that human sentience is an emergent property of the pattern-recognising aspect of the human brain turning inwards to recognise patterns within itself so it seems likely to me that any non-digital device with sufficient capacity would spontaneously generate emergent phenomena, which might be as comparatively simple as the motions of a flock of birds or might amount to a rudimentary intelligence.
I’m not sure quantum computing would produce that. It is an incredible concept, but it is still essentially operating within a digital paradigm of “on” and “off”, “true” and “false”, it’s just skipping a few steps to get to the answer, chucking out the occasional “maybe” that eventually resolves to either “true” or “false”.
I love the ruddy glow from the graphite plates of a pair of 813s. And they can keep the ham shack nice and toasty in the winter time. At RPI’s ham station W2SZ they had a single HV supply for all of the HF amps. It was in a caged room using a pole peg feeding 866 mercury rectifiers. Quite colorful.
Tom Bakewell KE7AVZ ex WB6HLR
The IGFET has been around for a long time. No breakthrough here just evolution as with any other semiconductor device. I remember the days when Ico was the bane of all transistor circuit designers.
Tube lovers:the transistor is here to stay. Get over it.
And don’t forget printed circuits are susceptible to static electricity. Once zapped their reliability goes out the window.
I’ve invented a vacuum tube filled with CO2. It operates at infra red and dosen’t need a heater.
It warms up due to back radiation which also produces the amplification.
Ok, just one more note about vacuum tubes;
Back in WWII (the BIG one per Archie Bunker) the USA developed (Lincoln Labs, MIT) a far superior fuse for the shells used in our big Army guns and Navy AA guns. This was a radar proximity fuse that sensed the approach of metallic or dense materials (i.e. Japanese Planes or the ground that German troops were standing on). Once the proximity to target was sensed the shell exploded.
Our enemies (friends now) only had time delay fuses and they actually adjusted them before firing for the altitude they thought our planes were at.
Our fuses were vastly superior, once we introduced them our rate of hits on the planes attacking our Navy went from a plane every few ten thousand shells to every hundred shells, or so.
The interesting thing is; those fuses had several miniature vacuum tubes inside. These were really tough tubes, the G forces from being fired out of a gun is tens – hundreds of G’s. But they survived the launch. All over the country people were assembling portions of these tubes without any idea what they were for.
So, in part we defeated the Japanese and Germans by firing vacuum tubes at them…………
Cheers, Kevin
Vacuum tubes live on! The venerable HW101 in my “3-generation shack”, on the left, and the signal scope above it are all tubed. 22 of them in the HW101. Other than having to replace the rubber drive belts in the mechanical tuner section from time to time, and try to remember how to properly “dip the finals” on tune up, it still warms the shack and tickles the neighbourhood.
http://ephemerata.wordpress.com/2009/09/01/beautiful-noise/
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…
Indeed, Mike, I had an old ’64 Fender Bassman head that was fantastic. I liked the look of the tubes as the 6L6s would die, they’d get all blue and plasma-y all the time. Unfortunately, they started sounding like crap about the same time. 😉
Couldn’t see the 12AX7 tubes in that amp, as they all had springloaded metal covers.
The only drawback was the REALLY BIG zap I got one time playing outdoors in the summer. I happened to be barefoot on concrete, and grabbed my guitar… ouchie. Got a couple of those through the lip grounding out on a microphone too, but not nearly as bad.
…. ahhh, the good old days.
That said, my back really appreciates the new technology that gives me a 300w rms power amp in a 2.5lb package, not to mention the neodymium magnets on speakers now…. Where’d my Doan’s pills go?
I haven’t had time to read the (amazingly heavy) barrage of responses
to the initial post, but of those I did read, I agree most strongly with
curiousgeorge. It has been some time now since SYSTEM speed was
dictated by DEVICE speed. The real challenge these days is getting a
‘fast’ signal from one place (say, the output of a gate) to another (the
input of the next gate, or – far worse, an output pin on an IC). That’s
to say, we live in an era in which electro(magnetic) propagation is in
the driver’s seat.
Years ago, I proposed planar triode, standing on the shoulders of all
the advances in CMOS technology. It’s a ‘low-hanging’ plum and not
very remarkable at all. But I knew very well that the only ‘good’ use
to which such a device could be applied was in space applications,
and that is still true- although, even THAT is a stretch, since modern
CMOS transistors using hafnium-doped gate stacks are also rad-hard.
Nevertheless, the realization of this idea is welcome news, even as a
curiosity. And it will doubtless have some uses.
My late father was an audio electronics engineer from the era of vacuum tubes all the way to solid state. Sadly he sold off all of his older tube audio stuff which is now sought after by collectors.
All my ham gear is solid state but one of these days I’m going to arrange to have Dad’s kilowatt Heathkit linear shipped to me. I mostly play acoustic guitars but I have a couple of electrics. I have a little solid state Fender amp. While back at my parents house several years ago I found the head unit of a 60s era Silvertone Twin Twelve tube amp. The speakers and the case were gone so I shipped it back home. I think it cost me a little over $150 to replace all the tubes. I even bought a pair of the (new) original 12″ Jensen speakers for authenticity. I have yet to find an original spring reverb. But it works and sounds great. It’s got that same sound I remember as kid when I was learning to play guitar. What really surprised me is the interest other musicians have in this amp. Must be that “tube sound.”
Jim says,
“You guys keep saying that, and yet commercial products put out by the likes such as Harris continue to supersede that oft-repeated “Solid-State Power Amplifiers are Limited” saw.”
True enough at HF and VHF frequencies such as VHF TV which is pretty much obsolete, but those commercial products use parallel of other configurations solid state devices to develope, say, 10 KW, whereas a single tube can easily provide many times that amount of power. Also, in the UHF and microwave range, solid state devices are much more expensive for high power applications, such as UHF TV, than are tubes. I sure have enjoyed the walk down memory lane with many of you here. I remember the “romance” of listening to far away short wave stations when I was 12 in 1952, and of getting my Novice ham ticket a couple years later. I don’t think young people have any sense of that kind of “romance” or anything comparable- or am I wrong?
Does not appear to be a vacuum tube. Merely a FET with a vacuum isolated gate.
Vacuum tubes emit electrons across the vacuum and steer them with space charges. This device appears to inject electrons from source silicon to drain silicon and controlled via charge in the gate channel silicon.
“Steve in SC says: May 24, 2012 at 4:27 pm Vacuum Tubes have always been superior to transistors at RF.
Check any TV or Radio station transmitter.”
Part of the reason for this is power. Bipolar transistors have always been able to handle more power than the more common MOSFET devices which actually operate similar to a vacuum tube. You will almost always find bipolar output transistors in high power solid state designs. And solid state microwave devices have been around for years. Even so, manufacturers continue to increase the power range of both bipolar and MOSFET devices and developing new devices that can handle more power such as BiCMOS which combines the advantages of both technologies.
Also, the device you show a cross section of still looks like a solid state device to me with a couple of vacuum wells. Other than breakdown voltage, I don’t know why that might be any better than a P/N junction.
Vacuum tubes. I remember Grandpa trying fix our TV in the early ’60’s. He pulled a few of the tubes out and let us go with him to Woolworths. They had a tester. You just plugged the questionable tube into the right socket to find out which one was bad. Replacements were on nearby shelves.
I also remember my brothers and I had an old phonograph in our room that had vacuum tubes. If we turned it a certain way and fiddled with one of the knobs, we could get WLW radio on it!
In The high tech world, we use an expression to explain the workings of some gadget that we don’t fully understand. We say: Oh, It works by FM. (the M stands for magic.)
Seriously though. These frequencies are very high. This is a switching device. on and off, 1 and 0, data.
Soon, the drivel of the internet coming to you even faster