Nanoplasma-enabled picosecond switches for ultrafast electronics

[Joe Gwinn]

The article is in Nature Magazine, 26 March 2020, pages 534-539, by
Nikoo et al. The device a bit of metal stripline on polyimide film,
immersed in air, and generates pulses at 10 MHz, about 12 picoseconds
wide, and 50-volt amplitude into 50 ohms. How is this done? It's
basically an old-time spark-gap transmitter in miniature. The metal
stripline has a very narrow gap where the microplasma forms, and acts
as a switch. Expected to work in the terahertz. Initial tests yield

.<https://www.nature.com/articles/s41586-020-2118-y>

Samizadeh Nikoo, M., Jafari, A., Perera, N. et al. Nanoplasma-enabled
picosecond switches for ultrafast electronics. Nature 579, 534–539
(2020). https://doi.org/10.1038/s41586-020-2118-y

Abstract: The broad applications of ultrawide-band signals and
terahertz waves in quantum measurements1,2, imaging and sensing
techniques3,4, advanced biological treatments5, and
very-high-data-rate communications6 have drawn extensive attention to
ultrafast electronics. In such applications, high-speed operation of
electronic switches is challenging, especially when high-amplitude
output signals are required7. For instance, although field-effect and
bipolar junction devices have good controllability and robust
performance, their relatively large output capacitance with respect to
their ON-state current substantially limits their switching speed8.
Here we demonstrate a novel on-chip, all-electronic device based on a
nanoscale plasma (nanoplasma) that enables picosecond switching of
electric signals with a wide range of power levels. The very high
electric field in the small volume of the nanoplasma leads to
ultrafast electron transfer, resulting in extremely short time
responses. We achieved an ultrafast switching speed, higher than 10
volts per picosecond, which is about two orders of magnitude larger
than that of field-effect transistors and more than ten times faster
than that of conventional electronic switches. We measured extremely
short rise times down to five picoseconds, which were limited by the
employed measurement set-up. By integrating these devices with dipole
antennas, high-power terahertz signals with a power–frequency
trade-off of 600 milliwatts terahertz squared were emitted, much
greater than that achieved by the state of the art in compact
solid-state electronics. The ease of integration and the compactness
of the nanoplasma switches could enable their implementation in
several fields, such as imaging, sensing, communications and
biomedical applications.

It's behind a paywall, but most libraries carry Nature.

Joe Gwinn

[pcdh...@gmail.com]

Wonder how they turn it off. Plasma recombination is schlooowwwww.

Cheers

Phil Hobbs

[John Larkin]

And does it wear out?

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

[Bill Sloman]

On Saturday, May 23, 2020 at 10:10:59 AM UTC+10, John Larkin wrote:
> On Fri, 22 May 2020 16:59:13 -0700 (PDT), pcdh...@gmail.com wrote:
>
> >Wonder how they turn it off. Plasma recombination is schlooowwwww.
>

> And does it wear out?

Almost certainly. Produce a plasma in air and you've got ozone and nitric oxide, which rapidly oxidises to nitrogen dioxide, which reacts with water vapour to make nitric acid.

For a while some place in Norway made nitrate fertiliser by blowing air through an electric arc and capturing nitrogen dioxide produced.

https://en.wikipedia.org/wiki/Birkeland%E2%80%93Eyde_process

Neither the polyimide substrate nor regular metal tracks would to last too long.

A teflon substrate and noble metal tracks might do better, but an air plasma is very aggressive.

If the gap is narrow enough and the electric field is high enough, the electrons might only be being generated by cold field emission, and might get across the gap without ionising too many oxygen or nitrogen molecules, but then you wouldn't have a plasma.

You would be looking at the high-field low-gap end of the Paschen curve

https://en.wikipedia.org/wiki/Paschen%27s_law

The authors of the Nature paper should know all about that, but might not bother telling their target audience.

--
Bill Sloman, Sydney

[John Miles, KE5FX]

On Friday, May 22, 2020 at 4:59:18 PM UTC-7, pcdh...@gmail.com wrote:
> Wonder how they turn it off. Plasma recombination is schlooowwwww.

Less than 20 ns, apparently. The paper is downloadable from
sci-hub.tw with DOI 10.1038/s41586-020-2118-y .

It's amusing how carefully the authors avoid using the term "spark
gap." I wonder if there's any way to create a sub-100 nm gap
without resorting to ion beam etching? J. C. Bose probably did it
in 1895, somehow...

-- john, KE5FX

[Bill Sloman]

Useful link.

"Townsend avalanche is the dominant plasma formation mechanism for
g > 5 μm, while field-effect emission and tunnelling are dominant for
5 nm < g < 5 μm, and g < 5 nm, respectively18. d, The higher electric field in a
shorter gap distance results in a much faster electron transport for
nanoplasma devices."

I suspect that their "nanoplasma" is just free electrons.

The mean free path of an electron in air seems to be about 500nm, which is the upper limit of the gaps being talked about, and the electron has to pick up 15.6 eV of energy to ionise a nitrogen molecule, and the fast switching still seems to be there at voltages below that.

--
Bill Sloman, Sydney

[Phil Hobbs]

Sure. You build it vertically and then cleave the wafer.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

[Bill Sloman]

On Sunday, May 24, 2020 at 12:05:26 AM UTC+10, Phil Hobbs wrote:
> On 2020-05-23 02:44, John Miles, KE5FX wrote:
> > On Friday, May 22, 2020 at 4:59:18 PM UTC-7, pcdh...@gmail.com wrote:
> >> Wonder how they turn it off. Plasma recombination is schlooowwwww.
> >
> > Less than 20 ns, apparently. The paper is downloadable from
> > sci-hub.tw with DOI 10.1038/s41586-020-2118-y .
> >
> > It's amusing how carefully the authors avoid using the term "spark
> > gap." I wonder if there's any way to create a sub-100 nm gap
> > without resorting to ion beam etching? J. C. Bose probably did it
> > in 1895, somehow...
> >

> Sure. You build it vertically and then cleave the wafer.

Doesn't seem to be what they've done.

The pictures are of something planar.

--
Bill Sloman, Sydney

[jla...@highlandsniptechnology.com]

Sparks gaps can dump megawatts in picoseconds. There's nothing else
like that.

NLTLs, shock lines, can do around 10 volts with rise times of a few
ps, and won't wear out.

--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

[Joe Gwinn]

On Fri, 22 May 2020 23:44:55 -0700 (PDT), "John Miles, KE5FX"
<jmi...@gmail.com> wrote:

>On Friday, May 22, 2020 at 4:59:18 PM UTC-7, pcdh...@gmail.com wrote:
>> Wonder how they turn it off. Plasma recombination is schlooowwwww.
>
>Less than 20 ns, apparently. The paper is downloadable from
>sci-hub.tw with DOI 10.1038/s41586-020-2118-y .
>
>It's amusing how carefully the authors avoid using the term "spark
>gap."

Yeah. When I saw the circuit, I had to laugh. When I was a teenager
in the 1950s, I found the following book in a curio store:

"Wireless Telegraphy", by Dr. J. Zenneck, translated fron the German
by A.E.Seelig, E.E., First Edition, McGraw-Hill 1915, 443 pages.

Still have it. All about Spark-gap transmitters, Poulsen Arcs,
Alexanderson Generators, and the like. Vacuum tube generators just
becoming practical, for small stuff. Alexanderson Generators are
still used in industry, to generate RF power for induction heating.

Joe Gwinn

[Joe Gwinn]

On Sat, 23 May 2020 09:35:45 -0700, jla...@highlandsniptechnology.com
wrote:

>On Fri, 22 May 2020 23:44:55 -0700 (PDT), "John Miles, KE5FX"
><jmi...@gmail.com> wrote:
>
>>On Friday, May 22, 2020 at 4:59:18 PM UTC-7, pcdh...@gmail.com wrote:
>>> Wonder how they turn it off. Plasma recombination is schlooowwwww.
>>
>>Less than 20 ns, apparently. The paper is downloadable from
>>sci-hub.tw with DOI 10.1038/s41586-020-2118-y .
>>
>>It's amusing how carefully the authors avoid using the term "spark
>>gap." I wonder if there's any way to create a sub-100 nm gap
>>without resorting to ion beam etching? J. C. Bose probably did it
>>in 1895, somehow...
>>
>>-- john, KE5FX
>
>Sparks gaps can dump megawatts in picoseconds. There's nothing else
>like that.

Oh yeah.

As for wear, if one were to do this for real, I'd guess that one would
build the devices of ceramic and a refractory metals, like hydrogen
thyratrons.

>NLTLs, shock lines, can do around 10 volts with rise times of a few
>ps, and won't wear out.

The spark gap can do 100 volts, no problem.

In frequency-multiplication service,NLTLs are 10 to 30 dB quieter than
SRDs, but expensive.

Joe Gwinn

[jla...@highlandsniptechnology.com]

On Sat, 23 May 2020 14:59:30 -0400, Joe Gwinn <joeg...@comcast.net>
wrote:

There have been some high-voltage NLTLs. The McEwan guy made them from
discrete inductors and diodes, nanosecond and kilovolt stuff. There
have also been some planar structures, metal strips on a slab of
nonlinear ceramic.

[Joe Gwinn]

On Sat, 23 May 2020 12:07:01 -0700, jla...@highlandsniptechnology.com

I recall those from McEwan. I was tempted to make one, but it was too
much work. If I recall, one needed 50 or 100 sections for it to work
well. A Blumelin line was easier:
<https://en.wikipedia.org/wiki/Pulse-forming_network>

Joe Gwinn

[Phil Hobbs]

Now free on archive.org:
<https://archive.org/details/in.ernet.dli.2015.212404>

(Not that anybody actually reads all the way through scanned e-books.) :(

[whit3rd]

On Friday, May 22, 2020 at 7:57:03 PM UTC-7, Bill Sloman wrote:
> On Saturday, May 23, 2020 at 10:10:59 AM UTC+10, John Larkin wrote:
> > On Fri, 22 May 2020 16:59:13 -0700 (PDT), pcdh...@gmail.com wrote:
> >
> > >Wonder how they turn it off. Plasma recombination is schlooowwwww.
> >
> > And does it wear out?
>
> Almost certainly. Produce a plasma in air and you've got ozone and nitric oxide, which rapidly oxidises to nitrogen dioxide, which reacts with water vapour to make nitric acid.

Thus, the vacuum-sealed mercury wetted relay is a popular variant,
if the small duty cycle isn't an issue.
Ozone, too, means that one doesn't want an airgapped set of points in the breathing air.

[John Miles, KE5FX]

On Saturday, May 23, 2020 at 7:05:26 AM UTC-7, Phil Hobbs wrote:
> Sure. You build it vertically and then cleave the wafer.

Having trouble visualizing this. Is there a diagram somewhere?

I tried cutting a slot in the top layer of a copper PCB strip using
a scalpel, the idea being to pinch it shut manually until it fires
somewhere near the bottom of the Paschen curve:

http://www.ke5fx.com/microgap/gap.jpg (closeup)
http://www.ke5fx.com/microgap/10x.jpg (test setup for HV edge)
http://www.ke5fx.com/microgap/50R.jpg (test setup for 50 ohms)

Driving it at -350V through a 100K resistor makes the gap fire somewhat
randomly at about 100 V/ns, limited by the probe and various strays.
The recovery time is also swamped by the scope probe RC:

http://www.ke5fx.com/microgap/mso_10x_probe_1us_div.png
http://www.ke5fx.com/microgap/mso_10x_probe_1ns_div.png

A 50-ohm series tap is faster, but likely still limited by strays:

http://www.ke5fx.com/microgap/mso_50R_1ns_div.png (MSO6054A, 500 MHz BW)
http://www.ke5fx.com/microgap/tds_50R_1ns.gif (TDS 694C, 3000 MHz BW)

I did see some edges closer to .35/3000 = 117 ps, but 164 ps was the
fastest one that I saved before the PCB strip finally broke.

-- john, KE5FX

[Phil Hobbs]

On 2020-05-23 18:13, John Miles, KE5FX wrote:
> On Saturday, May 23, 2020 at 7:05:26 AM UTC-7, Phil Hobbs wrote:
>> Sure. You build it vertically and then cleave the wafer.
>
> Having trouble visualizing this. Is there a diagram somewhere?

I haven't read the paper, because very small spark gaps aren't that
interesting--you can turn them on pretty fast, but (as in this case)
turning them off takes thousands of times longer, which makes them of
little interest in applications. (Not to mention their probably very
short lifetime.)

>
> I tried cutting a slot in the top layer of a copper PCB strip using
> a scalpel, the idea being to pinch it shut manually until it fires
> somewhere near the bottom of the Paschen curve:
>
> http://www.ke5fx.com/microgap/gap.jpg (closeup)
> http://www.ke5fx.com/microgap/10x.jpg (test setup for HV edge)
> http://www.ke5fx.com/microgap/50R.jpg (test setup for 50 ohms)
>
> Driving it at -350V through a 100K resistor makes the gap fire somewhat
> randomly at about 100 V/ns, limited by the probe and various strays.
> The recovery time is also swamped by the scope probe RC:
>
> http://www.ke5fx.com/microgap/mso_10x_probe_1us_div.png
> http://www.ke5fx.com/microgap/mso_10x_probe_1ns_div.png
>
> A 50-ohm series tap is faster, but likely still limited by strays:
>
> http://www.ke5fx.com/microgap/mso_50R_1ns_div.png (MSO6054A, 500 MHz BW)
> http://www.ke5fx.com/microgap/tds_50R_1ns.gif (TDS 694C, 3000 MHz BW)
>
> I did see some edges closer to .35/3000 = 117 ps, but 164 ps was the
> fastest one that I saved before the PCB strip finally broke.

You can get edges nearly that fast from a properly designed
mercury-wetted relay. One of Jim Williams's book chapters talks about
an ancient Tek pulser that worked that way. It's all about minimizing
inductance.

[Phil Hobbs]

On 2020-05-23 14:59, Joe Gwinn wrote:
> On Sat, 23 May 2020 09:35:45 -0700, jla...@highlandsniptechnology.com
> wrote:
>
>> On Fri, 22 May 2020 23:44:55 -0700 (PDT), "John Miles, KE5FX"
>> <jmi...@gmail.com> wrote:
>>
>>> On Friday, May 22, 2020 at 4:59:18 PM UTC-7, pcdh...@gmail.com wrote:
>>>> Wonder how they turn it off. Plasma recombination is schlooowwwww.
>>>
>>> Less than 20 ns, apparently. The paper is downloadable from
>>> sci-hub.tw with DOI 10.1038/s41586-020-2118-y .
>>>
>>> It's amusing how carefully the authors avoid using the term "spark
>>> gap." I wonder if there's any way to create a sub-100 nm gap
>>> without resorting to ion beam etching? J. C. Bose probably did it
>>> in 1895, somehow...
>>>
>>> -- john, KE5FX
>>
>> Sparks gaps can dump megawatts in picoseconds. There's nothing else
>> like that.
>
> Oh yeah.
>
> As for wear, if one were to do this for real, I'd guess that one would
> build the devices of ceramic and a refractory metals, like hydrogen
> thyratrons.

Barefoot thyratrons and krytrons aren't that fast--you need a
pulse-forming network such as a shock line.

>
>
>> NLTLs, shock lines, can do around 10 volts with rise times of a few
>> ps, and won't wear out.
>
> The spark gap can do 100 volts, no problem.
>
> In frequency-multiplication service,NLTLs are 10 to 30 dB quieter than
> SRDs, but expensive.

Interesting. My first task in my first engineering job (mid-1981) was
to rejigger an SRD multiplier to use a different diode. (The old diode
was self-biased with a bit of conductive ink, so I scribbled on the new
one with a soft pencil to find the right value--fun.)

However, I've never used a shock line multiplier. Do you have a
reference handy?

Thanks

[Michael Terrell]

On Saturday, May 23, 2020 at 5:05:41 PM UTC-4, Phil Hobbs wrote:
> On 2020-05-23 14:51, Joe Gwinn wrote:
> > On Fri, 22 May 2020 23:44:55 -0700 (PDT), "John Miles, KE5FX"
> > <jmi...@gmail.com> wrote:
> >
> >> On Friday, May 22, 2020 at 4:59:18 PM UTC-7, pcdh...@gmail.com wrote:
> >>> Wonder how they turn it off. Plasma recombination is schlooowwwww.
> >>
> >> Less than 20 ns, apparently. The paper is downloadable from
> >> sci-hub.tw with DOI 10.1038/s41586-020-2118-y .
> >>
> >> It's amusing how carefully the authors avoid using the term "spark
> >> gap."
> >
> > Yeah. When I saw the circuit, I had to laugh. When I was a teenager
> > in the 1950s, I found the following book in a curio store:
> >
> > "Wireless Telegraphy", by Dr. J. Zenneck, translated fron the German
> > by A.E.Seelig, E.E., First Edition, McGraw-Hill 1915, 443 pages.
> >
> > Still have it. All about Spark-gap transmitters, Poulsen Arcs,
> > Alexanderson Generators, and the like. Vacuum tube generators just
> > becoming practical, for small stuff. Alexanderson Generators are
> > still used in industry, to generate RF power for induction heating.
> >
> > Joe Gwinn
> >
> Now free on archive.org:
> <https://archive.org/details/in.ernet.dli.2015.212404>
>
> (Not that anybody actually reads all the way through scanned e-books.) :(

https://www.americanradiohistory.com/ is a huge collection of old Electronics magazines and books that were aimed at Hobbyists and professionals. All can be downloaded for free. They even have the four early Morgan books 'Radio book for Boys' My school had the first three, back in the '60s. I didn't know that there was a fourth book. Archive has a lot of old Amateur radio magazines, as well. These items were what fired my interest in Electronics as a kid. Instead of spending my allowance on candy or toys, I spent it on magazines. I still have a few of them, but most were lost or damaged while in storage over 30 years ago.

[Bill Sloman]

On Sunday, May 24, 2020 at 10:50:00 AM UTC+10, Phil Hobbs wrote:
> On 2020-05-23 18:13, John Miles, KE5FX wrote:
> > On Saturday, May 23, 2020 at 7:05:26 AM UTC-7, Phil Hobbs wrote:
> >> Sure. You build it vertically and then cleave the wafer.
> >
> > Having trouble visualizing this. Is there a diagram somewhere?
>
> I haven't read the paper, because very small spark gaps aren't that
> interesting--you can turn them on pretty fast, but (as in this case)
> turning them off takes thousands of times longer, which makes them of
> little interest in applications. (Not to mention their probably very
> short lifetime.)

https://doi.org/10.1038/s41586-020-2118-y

suggests that these gaps - which are very narrow - 1um down to 200nm - do turn off pretty quickly. The rise time is less than 1nsec (which is to say at least as fast as the 1GHz scope can measure), but this is shown with a 10MHz pulse train, so the nanoplasma has gone away in less than 50nsec.

It does look as if the authors "nanoplasma" is more like a burst of field-emission electrons. If they do produce any positive ions as they move through the air gap, those positive ions may capture electrons and remain electronically excited very briefly but they are in a very small volume and can lose energy pretty quickly.

I'd be interested in a high resolution image of edges of the gap. Field emission is enhanced at sharp points, and the edges of a metal gap are going to show their crystalline microstructure at this scale. Repeated operation may sharpen the points - arc discharges are sustained by field emission from a surface which has got hot enough to deform into a two dimensional array of spark spikes under the influence of a high electric field.

Arc lamps are physically a lot bigger and do tend to have tungsten electrodes - the centre of the arc is rather hotter than the surface of the sun.

The nano-gaps aren't going to get anything like as hot, but the metal at the surface of the gap may get warm enough to move around a bit (one atom at at time) when the electric field is high.

--
Bill Sloman, Sydney

[Joe Gwinn]

On Sat, 23 May 2020 20:56:17 -0400, Phil Hobbs
<pcdhSpamM...@electrooptical.net> wrote:

>On 2020-05-23 14:59, Joe Gwinn wrote:
>> On Sat, 23 May 2020 09:35:45 -0700, jla...@highlandsniptechnology.com
>> wrote:
>>
>>> On Fri, 22 May 2020 23:44:55 -0700 (PDT), "John Miles, KE5FX"
>>> <jmi...@gmail.com> wrote:
>>>
>>>> On Friday, May 22, 2020 at 4:59:18 PM UTC-7, pcdh...@gmail.com wrote:
>>>>> Wonder how they turn it off. Plasma recombination is schlooowwwww.
>>>>
>>>> Less than 20 ns, apparently. The paper is downloadable from
>>>> sci-hub.tw with DOI 10.1038/s41586-020-2118-y .
>>>>
>>>> It's amusing how carefully the authors avoid using the term "spark
>>>> gap." I wonder if there's any way to create a sub-100 nm gap
>>>> without resorting to ion beam etching? J. C. Bose probably did it
>>>> in 1895, somehow...
>>>>
>>>> -- john, KE5FX
>>>
>>> Sparks gaps can dump megawatts in picoseconds. There's nothing else
>>> like that.
>>
>> Oh yeah.
>>
>> As for wear, if one were to do this for real, I'd guess that one would
>> build the devices of ceramic and a refractory metals, like hydrogen
>> thyratrons.
>
>Barefoot thyratrons and krytrons aren't that fast--you need a
>pulse-forming network such as a shock line.

True enough, but the proposal is to implement the microplasma device
using materials proven in such things as thyratrons, and to get rid of
the oxygen atmosphere in the arc (or whatever the discharge is).

>>> NLTLs, shock lines, can do around 10 volts with rise times of a few
>>> ps, and won't wear out.
>>
>> The spark gap can do 100 volts, no problem.
>>
>> In frequency-multiplication service,NLTLs are 10 to 30 dB quieter than
>> SRDs, but expensive.
>
>Interesting. My first task in my first engineering job (mid-1981) was
>to rejigger an SRD multiplier to use a different diode. (The old diode
>was self-biased with a bit of conductive ink, so I scribbled on the new
>one with a soft pencil to find the right value--fun.)
>
>However, I've never used a shock line multiplier. Do you have a
>reference handy?

I do have some references, but it'll take me a while to find them.

In the mean time, a good source is the application notes and
datasheets from the current manufacturers, MACOM and Marki Microwave.
(Picosecond Labs is gone.)

The search term is "NLTL comb generator" (without the quotes).


.<https://www.macom.com/products/frequency-generation/nltl-gaas-comb-generators>

.<https://www.markimicrowave.com/blog/balanced-circuits-to-improve-frequency-comb-generation-with-nonlinear-transmission-lines/>

.<https://patents.google.com/patent/US7462956B2/en>

.<https://ui.adsabs.harvard.edu/abs/2018arXiv180202710L/abstract>

Found a few I didn't already know.

What's your application?

Joe Gwinn

[Phil Hobbs]

> ..<https://www.macom.com/products/frequency-generation/nltl-gaas-comb-generators>
>
> ..<https://www.markimicrowave.com/blog/balanced-circuits-to-improve-frequency-comb-generation-with-nonlinear-transmission-lines/>
>
> ..<https://patents.google.com/patent/US7462956B2/en>
>
> ..<https://ui.adsabs.harvard.edu/abs/2018arXiv180202710L/abstract>

>
> Found a few I didn't already know.
>
> What's your application?
>
> Joe Gwinn
>

None at the moment, but I get asked to do some pretty strange things, so
it's good to have stuff in the tool kit. ;)

Cheers