[math-fun] return of vacuum tube?
Jin-Woo Han & Meyya Meyyappan: Introducing the Vacuum Transistor: A Device Made of Nothing, IEEE Spectrum June 2014. J-W Han, Jae Sub Oh, M. Meyyappan: Vacuum nanoelectronics: Back to the future?--Gate insulated nanoscale vacuum channel transistor, Applied Physics Letters 100 (2012) 213505. What they call the "vacuum transistor" is actually a miniature vacuum tube. They point out that (a) if you make it very small (50 nanometers, say), you do not even need vacuum, since the path length before an electron hits a gas atom is smaller or comparable to the size of the tube. (b) you do not need a heated filament, since "field emission" from sharp corners of tiny pointed anodes is adequate. (c) you can fabricate it using micro-lithography techniques like those used to make silicon chips, constructing integrated circuits made of these vacuum tubes. (d) at low voltages using noble gas, there is not enough electron energy to ionize gas atoms, which supposedly prevents erosion of cathodes by ions. (e) might be more radiation-tolerant than semiconductor electronics. They've made these devices run at 460 GHz, which is way faster than solid state transistors can go. I also point out that (f) no more ultrapure single crystal low-defect silicon needed -- maybe can now use cheaper less-pure metal materials. I don't see why semiconductors are needed at all, although you might want hybrid circuit using both vacuum tubes and semiconductor devices, for example so you could have "flash RAM". This all sounded pretty promising to me. It seems possible to me this could speed up computer chip internals by factors 10-100 while also decreasing costs. Was the whole transistor approach the wrong approach? -- Warren D. Smith http://RangeVoting.org <-- add your endorsement (by clicking "endorse" as 1st step)
I’m glad to see this finally out in the open. I’ve been telling people this story for about 25 years. I actually think that there is a classified program using this technology — no one at DARPA would talk about it, and the advantages, as you suggest, are dramatic, especially the rad-hard aspects. Silicon is almost certainly the substrate of choice, given our extensive experience with fabricating it, and its excellent thermal characteristic. On Jul 15, 2014, at 8:24 PM, Warren D Smith <warren.wds@gmail.com> wrote:
Jin-Woo Han & Meyya Meyyappan: Introducing the Vacuum Transistor: A Device Made of Nothing, IEEE Spectrum June 2014. J-W Han, Jae Sub Oh, M. Meyyappan: Vacuum nanoelectronics: Back to the future?--Gate insulated nanoscale vacuum channel transistor, Applied Physics Letters 100 (2012) 213505.
What they call the "vacuum transistor" is actually a miniature vacuum tube. They point out that (a) if you make it very small (50 nanometers, say), you do not even need vacuum, since the path length before an electron hits a gas atom is smaller or comparable to the size of the tube. (b) you do not need a heated filament, since "field emission" from sharp corners of tiny pointed anodes is adequate. (c) you can fabricate it using micro-lithography techniques like those used to make silicon chips, constructing integrated circuits made of these vacuum tubes. (d) at low voltages using noble gas, there is not enough electron energy to ionize gas atoms, which supposedly prevents erosion of cathodes by ions. (e) might be more radiation-tolerant than semiconductor electronics.
They've made these devices run at 460 GHz, which is way faster than solid state transistors can go. I also point out that (f) no more ultrapure single crystal low-defect silicon needed -- maybe can now use cheaper less-pure metal materials.
I don't see why semiconductors are needed at all, although you might want hybrid circuit using both vacuum tubes and semiconductor devices, for example so you could have "flash RAM".
This all sounded pretty promising to me. It seems possible to me this could speed up computer chip internals by factors 10-100 while also decreasing costs. Was the whole transistor approach the wrong approach?
-- Warren D. Smith http://RangeVoting.org <-- add your endorsement (by clicking "endorse" as 1st step)
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Another advantage occurs to me: (g) Thermal immunity. That is, it seems to me that a device based on these micro-vacuum-tubes, if designed right, could work at any temperature from, say, 0 kelvin to 600 kelvin. It would work on Venus. Meanwhile semiconductors are highly affected by temperature changes because more (or less) dopant atoms are ionized at higher (lower) temperatures. So long as the temperature was well below melting points and metal "work function" levels needed to allow substantial thermionic emission, these devices ought to work in a temperature-independent manner. Old-style vacuum tubes used heated filaments and anodes made of special low-work-function materials. The new idea should not need such materials. I'm fascinated by Tom Knight implying this whole idea was around for a long time but classified secret. The inventors I cited seemed to think it was their own idea, and they worked at NASA. If this is truly a great idea, and it truly was suppressed for decades by secrecy... that seems yet another severe indictment of the whole secrecy system...
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Tom Knight -
Warren D Smith