5 ms·

> 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

by 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 ago
  I 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 ago
I 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 ago
  You mean ions/electrons between electrodes are deflected by voltage applied at the gate, as in vacuum tube?
- mannykannot 8y ago
  There 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 ago
  Oh, 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 ago
    It 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.)
deleted 8y ago
[deleted]
Thorondor 8y ago
In 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 ago
I'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 ago
The 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 ago
  Correcting 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.

by magnat 8y ago

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 ago
I 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 ago

I 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 ago
You mean ions/electrons between electrodes are deflected by voltage applied at the gate, as in vacuum tube?
mannykannot 8y ago
There 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 ago
Oh, 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 ago
  It 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.)

deleted 8y ago

[deleted]

Thorondor 8y ago

In 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 ago

I'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 ago

The 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 ago
Correcting 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.