10 ms·
New Metal-Air Transistor Replaces Semiconductors
- magnat 8y ago> It uses two in-plane symmetric metal electrodes separated by an air gap of less than 35 nanometers With air dielectric strength of 3kV/mm, why wouldn't such electrodes continously arc over when applied voltage is over 0.1V?
- twic 8y ago> The nanoscale air gap is less than the mean-free path of electrons in air, hence electrons can travel through air under room temperature without scattering. The device is so small that air needs to be thought of like ping-pong balls bouncing around inside a lottery machine, not a homogeneous bulk. Does that mean things like arc formation work differently? I honestly don't know!
- mannykannot 8y agoI get the impression that the gas molecules are not being ionized, the electrons merely pass between them. Thinking some more about this, does not dielectric breakdown in gases depend on electrons gaining sufficient energy to cause ionization in collisions with the molecules [1]? With the gap well below the mean free path, perhaps they cannot reach that speed at the voltages being used? [1] https://en.wikipedia.org/wiki/Paschen's_law#Physical_mechanism https://en.wikipedia.org/wiki/Paschen's_law#Physical_mechani...
- starbeast 8y agoI think that is the general idea, the field below regulates that arc. edit - This design is so absurdly straight forward, I am genuinely impressed. The damn thing is even reversible. Is cool as hell that this works. I wonder what the pitfalls are? edit2 for magnat as it is not letting me reply to the comment below - The way I understand it (given it is described as a FET), those two electrodes sit directly on top of a gate. If you flood the gate with electrons, then the gate's negative electric field will keep the electrons in the electrodes away from the gap, reducing or completely halting the flow of current.
- magnat 8y agoYou mean ions/electrons between electrodes are deflected by voltage applied at the gate, as in vacuum tube?
- mannykannot 8y agoThere is mention of one issue - melting of the tips. They are working on modifying the collector to reduce the stress on the emitter, which suggests that a practical device will not be reversible. (from a sufficiently abstract point of view, transistors appear to be reversible too, but in practice they are not.)
- anon_cow1111 8y agoOh, wow, this is basically a chip full of trigatrons isn't it? https://en.wikipedia.org/wiki/Trigatron https://en.wikipedia.org/wiki/Trigatron For anyone who doesn't feel like reading the wiki, these things are normally switches you use when all other types of switch would be destroyed by the amount of current you're trying to pass (the pictured device has a mesh cage to catch fragments if it blows up). If you've ever seen one of those demos where someone 'shrinks' a quarter or crushes cans with magnetic fields, there's a good chance that's what they're using to switch the power on. Seeing the same concept used in a cpu is bizarre, but really exciting if it works.
- marcosdumay 8y agoIt does not seem to use arcs, so it does not use a trigger. It's more suitable to think about this as a triode valve or a FET where the the channel is made of vacuum instead of silicon. (And only comes on N variety, what is not great.)
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- Thorondor 8y agoIn general, the dielectric strength of a gas varies with the gap length, so for small gaps it's not strictly correct to say that air has a dielectric strength of 3 kV/mm or any other single value. [0] But at this scale, the gap is so small that the idea of "dielectric strength" isn't really meaningful anyway. There are so few atoms between the electrodes that electrons can flow with negligible resistance at any reasonable field strength. [0] https://en.wikipedia.org/wiki/Paschen%27s_law https://en.wikipedia.org/wiki/Paschen%27s_law
- Zenst 8y agoI'd also wonder at the thermal properties and with a gap of 35nm, these would make chips large again. However, I suspect they would need to do vertical placement to allow the gap to be large enough without stepping back in silicon real estate. However, the question then becomes more important about the thermal properties of such an approach.
- T-A 8y agoThe first ionization energies of oxygen, nitrogen etc are all > 10 eV [1]. If you accelerate an electron over 35 nm with a 1 V electric field, it picks up 35e-9 eV. So it can't ionize anything, even if it happens to collide with a molecule, which is unlikely [2]. [1] http://www-personal.umich.edu/~cowley/ionen.htm http://www-personal.umich.edu/~cowley/ionen.htm [2] https://en.wikipedia.org/wiki/Mean_free_path https://en.wikipedia.org/wiki/Mean_free_path
- T-A 8y agoCorrecting myself: if you accelerate an electron through a potential difference of 1 V, it picks up 1 eV and nothing else. While the conclusion stands (it can't ionize anything), I plead temporary insanity for the way I arrived at it.
- twic 8y agoA few random thoughts: * Air presumably doesn't mean atmospheric air here, otherwise you're getting a random mix of gases and water vapour inside your nanoscale wizardry - so will these be nitrogen-filled, like binoculars etc? * What does this mean for cooling, especially in the high-density 3D architectures mentioned? Can you use air flow through the chip to cool it? * "tungsten, gold, and platinum were evaluated as metals of choice" - compare their resistivities of 5.60e-8, 2.44e-8, and 1.06e-7 ohm-metres respectively to silicon's of 6.4e+2 [1] (i thought tungsten was much higher than that, TIL). Does this mean that chips would have less resistive heating? Is resistive heating a significant part of the TDP of a modern chip? * "replacing silicon with metal means these ACT devices can be fabricated on any dielectric surface, provided the underlying substrate allows effective modulation of emission current from source to drain with a bottom-gate field" - is there is also a lattice-spacing constraint, where the substrate's spacing has to work with that of the conductor, as i believe there is with silicon chips? * Is this basically the return of the thermionic valve after fifty years in the wilderness? [1] https://en.wikipedia.org/wiki/Electrical_resistivity_and_conductivity#Resistivity_and_conductivity_of_various_materials https://en.wikipedia.org/wiki/Electrical_resistivity_and_con...
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- jakobegger 8y ago> Does this mean that chips would have less resistive heating? No. The parts of the chip that conduct electricity to the active areas in current chips are already made from metal. Basic chips are made from layers of metal / oxide / semiconductor (MOS). Current flows through silicon only in small areas, and the way chips work is that you can "turn off" the high resistivity in those areas and make them conducting (by doping the material + applying electric currents & fields) In the presented work, an air gap is used for these "active areas" instead of a semiconductor. An air gap does have resistance, so there will be resistive heating just like in normal chips.
- ArtifTh 8y agoSo, basically a nanoscale electron tube?
- blattimwind 8y agoExcept without a vacuum (because the plate distance is so small that air doesn't get in the way)
- madengr 8y agoI wonder what happened to cold cathode display technology. It’s similar in that electrons are coaxed off a sharp tip. This would have the benefit of a controlling gate.
- mabbo 8y agoAs a general rule, anytime an article is titled with a question I presume the answer to be "No".
- Gh0stRAT 8y agoBettridge's Law of Headlines https://en.m.wikipedia.org/wiki/Betteridge's_law_of_headlines https://en.m.wikipedia.org/wiki/Betteridge's_law_of_headline...
- Nasrudith 8y agoI would say it is probably yes to the first and no to the second with a caveat - just because you can doesn't necessarily mean that you should. You can power your cellphone on an integral kerosene fuel cell but it doesn't really make sense to do so except maybe in very narrow circumstances. Not that you shouldn't but a lot of potential advanced techniques fall in and out of favor like how CMOS went from power efficent electronics to the way as power efficiency dominated over gate efficiency.
- starbeast 8y agoIs Betteridge's Law Of Headlines Always Correct? Find out in our article below...
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- api 8y agoI find heuristics like this to be anti-intellectual. In news orgs the person who picks the headline often isn't even the person who wrote the article.
- rlpb 8y agoThe person who picks a headline like this is generally trying to create the most attention with it without making a false statement. Instead of "Can New Metal-Air Transistors Replace Semiconductors and Continue Moore's Law?", the headline writer would love to write "New Metal-Air Transistors Replace Semiconductors and Continue Moore's Law". That would be more effective. The fact that the headline writer could not say this tells us something. The same goes for weasel words like "may". > I find heuristics like this to be anti-intellectual. It is absolutely appropriate to detect what might have been said but was not, consider the motivations of the speaker, and infer non-importance appropriately.
- liftbigweights 8y agoWhat happened to graphene? A couple of years ago, that's all anyone talked about? I thought graphene was going to get us back on the exponential incline that is moore's law? I'm guessing the answer is no ( betteridge's law ) and we are going to stay in the multi-core environment for a while. 128, 256, 512, 1024, ... cores. Though I suspect that is going to run into problems very quickly.
- wyoh 8y agoMight be why: http://blogs.sciencemag.org/pipeline/archives/2018/10/11/graphene-you-dont-get-what-you-pay-for http://blogs.sciencemag.org/pipeline/archives/2018/10/11/gra...
- amacbride 8y ago“The only thing graphene can’t do is make it out of the lab.”
- amacbride 8y ago(I took the Stanford nanoscale materials science class this summer, and we all had a good laugh. Graphene is very interesting, but it’s subject to the hype cycle.)
- cultofmetatron 8y agoProgress is being made. The price of graphene has come down a lot in recent years. There's a new process by which you can coat a cd with graphite oxide and selectively burn paths of graphene with a LightScribe laser. At this point its pretty trivial to create flakes of graphene at home with some basic chemistry equipment. (enough to make your own 1 farad supercapacitor!) https://www.youtube.com/watch?v=t-LMZHIdwC8 https://www.youtube.com/watch?v=t-LMZHIdwC8
- jpmattia 8y agoAs you might expect, this is more of an engineering press release and not a balanced technical discussion. Two things jump out at me: > The nanoscale air gap is less than the mean-free path of electrons in air, hence electrons can travel through air under room temperature without scattering. Electron transport without scattering is usually termed "ballistic transport", and as gate sizes shrink in traditional MOS devices, a larger fraction of channel electrons make it across the channel before scattering. So maybe air gaps might speed up the arrival of mass-production ballistic transistors. However, there is a new problem: To get an electron out of the metal, you need to kick it up to the vacuum level (the electron work function of the material). Giving energy to the electron to get it out of the metal was the reason that tubes had heating elements back in the day. In more modern research, it's the reason why people have been exploring diamond thin-film emitters: It turns out that diamond has the interesting property that the conduction band is above the vacuum level (!), which means that a conduction-band electron will fall out of the material given the chance. (Surface physics gets in the way, which is why diamond engagement rings aren't positively charged rocks, but very cool nevertheless.) Alternatively, you need to apply an electric field to have electrons tunnel out, but usually that corresponds to a very large field where other bad things start to happen (breakdown, electromigration, etc) > Because the electrons flow between the electrodes just as well in a vacuum (think vacuum tube) as in air, radiation will not modulate channel properties, making ACT devices suitable for use in extreme radiation environments and space. When radiation from space goes through an MOS-type device, there are two big problems: 1. Ionizing radiation in the channel creates electron-hole pairs, which creates excess current between source and drain temporarily, 2. Ionizing radiation in the dielectric creates electron-hole pairs in the gate, and often the hole gets trapped in the gate leading to a permanent threshold shift. This eventually causes failure, and is usually the bigger problem when designing a space-qualified process. So while "radiation will not modulate channel properties" is maybe technically right, the press release is ignoring that the radiation will still modulate gate properties, which will in turn modulate channel properties.
- neltnerb 8y agoThis design also struck me as a non-tunneling version of a single electron transistor. Stick a 10nm metal island in the middle, make the spacing bigger, and it would look the same. Are the electric fields required really so big?
- tonmoy 8y agoI’m not clear where the transistor action is coming from? If it is indeed a transistor then leakage and gain numbers would be good to see
- tim333 8y agoThere's a clearer diagram here https://imgur.com/a/h6INwsu https://imgur.com/a/h6INwsu You put a voltage on the gate and the field it produces varies the current between the two metal bits.
- jl2718 8y agoThis article explains it better: https://spectrum.ieee.org/semiconductors/devices/introducing-the-vacuum-transistor-a-device-made-of-nothing https://spectrum.ieee.org/semiconductors/devices/introducing...
- btown 8y agoReally intriguing! I found https://www.engineering.com/ElectronicsDesign/ElectronicsDesignArticles/ArticleID/16337/Vacuum-Tubes-The-World-Before-Transistors.aspx https://www.engineering.com/ElectronicsDesign/ElectronicsDes... to be a useful companion to explain more about how control grids work in traditional vacuum tubes.
- jimbo1qaz 8y agoThe link was published in 2014, has technology advanced since then?
- dogma1138 8y agoSo basically back to vacuum tubes?
- klyrs 8y agoPretty much exactly that. Only... the environment is hot enough that (a) you don't need a heater, and even more interesting, (b) 1 atmosphere is an effective vacuum for features of that size. Amusingly, it sounds like these devices will be susceptible to helium poisoning. This all makes me wanna stop playing with superconductors and start playing with tubes again...
- PopeDotNinja 8y agoYou know this is a pretty new idea when googling "metal-air transistors" links to the posted article and this HN thread, and searching for the same term on YouTube reveals no videos (that I could recognize as being about this topic). Hey SciShow and/or Computerphile, we need videos to give us the TL;DR on metal-air transistors!
- MrEldritch 8y agoHere's an older article from IEEE reporting on an earlier version of the same technology - https://spectrum.ieee.org/semiconductors/devices/introducing-the-vacuum-transistor-a-device-made-of-nothing https://spectrum.ieee.org/semiconductors/devices/introducing... This one goes into somewhat greater technical detail.
- adrianratnapala 8y agoCan someone explain why the electrodes have to be sharp? Intuitively it feels right, but what is the actual reason? As far as I can see, the challenge is to get the E-fields (aka voltage gradients) high enough that electrons can easily leave the metal. But for that you need the electrodes close to one another, but they don't have to be sharp. I suppose if you have too big an area of metal at near-contact, then you will get unwanted capacitance. But is that the only reason?
- zamalek 8y agoError margins? There's a lot more room for error with a flat surface. I'm not sure if that level of precision is at all important, but it's my best guess.
- okl 8y agoProbably, because it results in a higher field strength at the tip, see https://www.physicsclassroom.com/class/estatics/u8l4d.cfm#p8 https://www.physicsclassroom.com/class/estatics/u8l4d.cfm#p8
- murbard2 8y agoThey do have to be sharp. As an exercise, consider a metallic cone with a charge of 1 and look at the distribution of the charge that minimizes the electrostatic energy. You will find that the charge collects near the tip of the cone. In general, charges will collect where the curvature is high. It's easier to push electrons out of a pointy tip (or inside of a pointy tip) because they are denser there.
- YetAnotherNick 8y agoApart from other answers, I think cold welding might be one reason too.