Reply by Phil Hobbs ●November 6, 20172017-11-06
On 11/04/2017 05:29 PM, amdx wrote:

> On 11/4/2017 11:16 AM, Phil Hobbs wrote:
>> On 11/04/2017 10:58 AM, Phil Hobbs wrote:
>>> On 11/04/2017 03:56 AM, Jan Panteltje wrote:
>>>> On a sunny day (Fri, 3 Nov 2017 16:58:22 -0500) it happened "Tim
>>>> Williams"
>>>> <tmoranwms@gmail.com> wrote in <otiop9$chs$1@dont-email.me>:
>>>>
>>>>> "Steve Wilson" <no@spam.com> wrote in message
>>>>> news:XnsA822AB7D5D5F6idtokenpost@69.16.179.23...
>>>>>> What causes the erosion? Is it the high voltage used?
>>>>>>
>>>>>> I'm not trying to prove you wrong. I'm trying to understand what the
>>>>>> mechanism is in case it has any bearing on some of my other projects.
>>>>>>
>>>>>> As I stated earlier, I could find no reference to tip erosion except
>>>>>> that
>>>>>> caused by ion impact damage or operation at high voltage. There was
>>>>>> nothing
>>>>>> on tip erosion at low voltages.
>>>>>>
>>>>>
>>>>> What's the physics at work, anyway?
>>>>>
>>>>> One would suppose the required voltage is proportional to the binding
>>>>> energy
>>>>> and/or work function of the material, and so tungsten would be the
>>>>> best.
>>>>> But those are infinite and ideal properties.
>>>>>
>>>>> One needs to take into account the boundary conditions, which are
>>>>> quite
>>>>> significant in an atomic-scale point.&#4294967295; The band structure will be very
>>>>> different in that region (annular confinement modes, where the band
>>>>> splits
>>>>> into discrete levels spaced according to the dimensions of the tip?),
>>>>> and
>>>>> maybe that leads to weakening of the material (a zone of low electron
>>>>> density acting as a stress raiser?).&#4294967295; One would then suppose, there
>>>>> exists
>>>>> an ideal tip shape which maximizes its minimum binding energy, while
>>>>> minimizing the work function or electron tunneling probability.
>>>>> Maybe it's
>>>>> a surface of rotation, with a funny curved profile; maybe it's not
>>>>> round,
>>>>> but polygonal; maybe it's a stepped cylinder, or pyramid or cone;
>>>>> maybe it's
>>>>> even hollow, or filled with other elements!
>>>>>
>>>>> Would be interesting to see some analysis of this ... but wouldn't
>>>>> be so
>>>>> interested as to dare attempt it myself. :-x
>>>>>
>>>>> Tim
>>>>
>>>> Some time ago there was some commotion about companies giving up on
>>>> field emission display tech,
>>>> selling of patents to other companies.
>>>> I do not see many of those displays for sale, none AFAIK.
>>>> At high field strength (due to small sizes) you are asking for trouble,
>>>> things will be ripped of the surface.
>>>>
>>>> And 460 GHz is not realy that fast, just a quick search with Bing:
>>>> &#4294967295;&#4294967295; Silicon-germanium (SiGe) transistor at 798 gigahertz (GHz) fMAX:
>>>> &#4294967295;&#4294967295;
>>>> http://www.news.gatech.edu/2014/02/17/silicon-germanium-chip-sets-new-speed-record
>>>>
>>>>
>>>>
>>>> NASA, they also have a prototype warp drive...
>>>> sigh
>>>
>>> Fun.&#4294967295; I knew John Cressler at IBM Watson--I took a BJT design course
>>> from him back in about 1988, when IBM was still building mainframes out
>>> of ECL.
>>>
>>> Re: field emitters
>>>
>>> Just in order to get an output power level above the Johnson noise of 50
>>> ohms in a 460 GHz bandwidth, you need
>>>
>>> Pout > -204 dBW + 10 log(460 GHz) = -87 dBW (2 nW).
>>>
>>>
>>> The RMS current in 50 ohms is I = sqrt(50* 2nW) = 300 uA.
>>
>> Never mind.&#4294967295; Note to self: don't post before having coffee.
>>
>> Should be sqrt(2 nW/50) = 6 uA.
>>
>>>
>>> With a transconductance of 20 nS/um (quoted by the Pittsburgh guys in
>>> Nature,
>>> https://www.nature.com/nnano/journal/v7/n8/full/nnano.2012.107.html,
>>> you'd need a device with gate width
>>>
>>> W > 300 uA/(20 nA/um) = 15000 um (15 mm).
>>
>> W > 6 uA/(20 nA/V/um) = 300 um, assuming 1V worth of grid drive.&#4294967295; Of
>> course that's with 1V of grid swing, so the voltage gain is about 0.0003
>> (50 ohms times 6 uA / 1V).
>>
>> To get actual voltage gain, it would have to be much, much bigger.&#4294967295; To
>> reach a voltage gain of 1.0 (20 mA plate current @ 1V grid drive) it
>> would need to be
>>
>> W > 20 mA / (20 nA/um/V * 1 V) = 1,000,000 um = 1 meter wide, which is
>> about 1500 wavelengths at 460 GHz.
>>
>> And that's not counting the capacitance, which for something that size
>> would be in the tens of picofarads.
>>
>> So just getting a voltage gain of 1.0 in 50 ohms at 460 GHz would
>> require quite the distributed amplifier structure, assuming you could
>> keep the losses low enough even to get near there.
>>
>> Cheers
>>
>> Phil Hobbs
>>
> &#4294967295;I see you are all po-poing the Idea then say it is not really that
> fast, on the other hand with only ONE built, not much optimizing has
> happened.


I'm not pooh-poohing anything.

I spent six years of my life bringing a niche research device (the
metal-insulator-metal tunnel junction) from a free-space curiosity at
0.01% quantum efficiency at a useless wavelength (10.7 um) to
technologically interesting efficiencies (7% quantum efficiency) coupled
to waveguides at telecom wavelengths (1.6 um), so I'm generally in
sympathy with that sort of effort.

What I'm not in sympathy with is the hype machine.  They claim 460 GHz,
forsooth, when the gizmo can't drive its own plate capacitance at even
1% of that rate.

My point is that it's pretty silly to start talking about applications
of a device when the current best is so very far off practicality, or to
talk about speed when it's essentially impossible to use the present
best version even to reach a gain of 1.0.

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
Reply by amdx ●November 4, 20172017-11-04
On 11/4/2017 11:16 AM, Phil Hobbs wrote:

> On 11/04/2017 10:58 AM, Phil Hobbs wrote:
>> On 11/04/2017 03:56 AM, Jan Panteltje wrote:
>>> On a sunny day (Fri, 3 Nov 2017 16:58:22 -0500) it happened "Tim
>>> Williams"
>>> <tmoranwms@gmail.com> wrote in <otiop9$chs$1@dont-email.me>:
>>>
>>>> "Steve Wilson" <no@spam.com> wrote in message
>>>> news:XnsA822AB7D5D5F6idtokenpost@69.16.179.23...
>>>>> What causes the erosion? Is it the high voltage used?
>>>>>
>>>>> I'm not trying to prove you wrong. I'm trying to understand what the
>>>>> mechanism is in case it has any bearing on some of my other projects.
>>>>>
>>>>> As I stated earlier, I could find no reference to tip erosion except
>>>>> that
>>>>> caused by ion impact damage or operation at high voltage. There was
>>>>> nothing
>>>>> on tip erosion at low voltages.
>>>>>
>>>>
>>>> What's the physics at work, anyway?
>>>>
>>>> One would suppose the required voltage is proportional to the binding
>>>> energy
>>>> and/or work function of the material, and so tungsten would be the best.
>>>> But those are infinite and ideal properties.
>>>>
>>>> One needs to take into account the boundary conditions, which are quite
>>>> significant in an atomic-scale point.&#4294967295; The band structure will be very
>>>> different in that region (annular confinement modes, where the band
>>>> splits
>>>> into discrete levels spaced according to the dimensions of the tip?),
>>>> and
>>>> maybe that leads to weakening of the material (a zone of low electron
>>>> density acting as a stress raiser?).&#4294967295; One would then suppose, there
>>>> exists
>>>> an ideal tip shape which maximizes its minimum binding energy, while
>>>> minimizing the work function or electron tunneling probability.
>>>> Maybe it's
>>>> a surface of rotation, with a funny curved profile; maybe it's not
>>>> round,
>>>> but polygonal; maybe it's a stepped cylinder, or pyramid or cone;
>>>> maybe it's
>>>> even hollow, or filled with other elements!
>>>>
>>>> Would be interesting to see some analysis of this ... but wouldn't be so
>>>> interested as to dare attempt it myself. :-x
>>>>
>>>> Tim
>>>
>>> Some time ago there was some commotion about companies giving up on
>>> field emission display tech,
>>> selling of patents to other companies.
>>> I do not see many of those displays for sale, none AFAIK.
>>> At high field strength (due to small sizes) you are asking for trouble,
>>> things will be ripped of the surface.
>>>
>>> And 460 GHz is not realy that fast, just a quick search with Bing:
>>>  &#4294967295; Silicon-germanium (SiGe) transistor at 798 gigahertz (GHz) fMAX:
>>>    
>>> http://www.news.gatech.edu/2014/02/17/silicon-germanium-chip-sets-new-speed-record
>>>
>>>
>>> NASA, they also have a prototype warp drive...
>>> sigh
>>
>> Fun.&#4294967295; I knew John Cressler at IBM Watson--I took a BJT design course
>> from him back in about 1988, when IBM was still building mainframes out
>> of ECL.
>>
>> Re: field emitters
>>
>> Just in order to get an output power level above the Johnson noise of 50
>> ohms in a 460 GHz bandwidth, you need
>>
>> Pout > -204 dBW + 10 log(460 GHz) = -87 dBW (2 nW).
>>
>>
>> The RMS current in 50 ohms is I = sqrt(50* 2nW) = 300 uA.
> 
> Never mind.  Note to self: don't post before having coffee.
> 
> Should be sqrt(2 nW/50) = 6 uA.
> 
>>
>> With a transconductance of 20 nS/um (quoted by the Pittsburgh guys in
>> Nature,
>> https://www.nature.com/nnano/journal/v7/n8/full/nnano.2012.107.html,
>> you'd need a device with gate width
>>
>> W > 300 uA/(20 nA/um) = 15000 um (15 mm).
> 
> W > 6 uA/(20 nA/V/um) = 300 um, assuming 1V worth of grid drive.  Of
> course that's with 1V of grid swing, so the voltage gain is about 0.0003
> (50 ohms times 6 uA / 1V).
> 
> To get actual voltage gain, it would have to be much, much bigger.  To
> reach a voltage gain of 1.0 (20 mA plate current @ 1V grid drive) it
> would need to be
> 
> W > 20 mA / (20 nA/um/V * 1 V) = 1,000,000 um = 1 meter wide, which is
> about 1500 wavelengths at 460 GHz.
> 
> And that's not counting the capacitance, which for something that size
> would be in the tens of picofarads.
> 
> So just getting a voltage gain of 1.0 in 50 ohms at 460 GHz would
> require quite the distributed amplifier structure, assuming you could
> keep the losses low enough even to get near there.
> 
> Cheers
> 
> Phil Hobbs
> 

  I see you are all po-poing the Idea then say it is not really that 
fast, on the other hand with only ONE built, not much optimizing has 
happened.
  But then, I thought LENR was going somewhere, all it became is an $89 
million lawsuit.
  Hmm, looks like it was settled.
  "No details of the settlement are available because Rossi and 
Industrial Heat have apparently signed a non-disclosure agreement (NDA)."

> http://coldfusion3.com/blog/rossi-industrial-heat-lawsuit-settled
Reply by Tim Williams ●November 4, 20172017-11-04
"Steve Wilson" <no@spam.com> wrote in message 
news:XnsA822BAEC427B6idtokenpost@69.16.179.22...

> It does not discuss tip erosion. A few articles I found say the electric
> field exceeds the binding energy of the atom, so it separates from the 
> tip.
>
> This means that high voltage and a sharp tip are needed. This has been my
> biggest problem from the beginning, since I thought I needed high voltage
> for electron emission, but I worried it would cause tip erosion and ozone
> generation. However, if I can get sufficient electron emission at low
> voltage as described in the IEEE article, that should reduce tip erosion
> and ozone generation. I'm going to give it a try.



It could very well be that no one has tried to run the numbers, whether it's 
solving the condensed matter structure (known to be a hard problem, no 
matter how you cut it), or doing the experiments.

Could also be that it's a negative result and so no one published their 
findings.

Either way, do report your findings, somewhere!

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: https://www.seventransistorlabs.com/
Reply by John Larkin ●November 4, 20172017-11-04
On Sat, 4 Nov 2017 12:16:38 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:


>On 11/04/2017 10:58 AM, Phil Hobbs wrote:
>> On 11/04/2017 03:56 AM, Jan Panteltje wrote:
>>> On a sunny day (Fri, 3 Nov 2017 16:58:22 -0500) it happened "Tim
>>> Williams"
>>> <tmoranwms@gmail.com> wrote in <otiop9$chs$1@dont-email.me>:
>>>
>>>> "Steve Wilson" <no@spam.com> wrote in message
>>>> news:XnsA822AB7D5D5F6idtokenpost@69.16.179.23...
>>>>> What causes the erosion? Is it the high voltage used?
>>>>>
>>>>> I'm not trying to prove you wrong. I'm trying to understand what the
>>>>> mechanism is in case it has any bearing on some of my other projects.
>>>>>
>>>>> As I stated earlier, I could find no reference to tip erosion except
>>>>> that
>>>>> caused by ion impact damage or operation at high voltage. There was
>>>>> nothing
>>>>> on tip erosion at low voltages.
>>>>>
>>>>
>>>> What's the physics at work, anyway?
>>>>
>>>> One would suppose the required voltage is proportional to the binding
>>>> energy
>>>> and/or work function of the material, and so tungsten would be the best.
>>>> But those are infinite and ideal properties.
>>>>
>>>> One needs to take into account the boundary conditions, which are quite
>>>> significant in an atomic-scale point.&#4294967295; The band structure will be very
>>>> different in that region (annular confinement modes, where the band
>>>> splits
>>>> into discrete levels spaced according to the dimensions of the tip?),
>>>> and
>>>> maybe that leads to weakening of the material (a zone of low electron
>>>> density acting as a stress raiser?).&#4294967295; One would then suppose, there
>>>> exists
>>>> an ideal tip shape which maximizes its minimum binding energy, while
>>>> minimizing the work function or electron tunneling probability.&#4294967295;
>>>> Maybe it's
>>>> a surface of rotation, with a funny curved profile; maybe it's not
>>>> round,
>>>> but polygonal; maybe it's a stepped cylinder, or pyramid or cone;
>>>> maybe it's
>>>> even hollow, or filled with other elements!
>>>>
>>>> Would be interesting to see some analysis of this ... but wouldn't be so
>>>> interested as to dare attempt it myself. :-x
>>>>
>>>> Tim
>>>
>>> Some time ago there was some commotion about companies giving up on
>>> field emission display tech,
>>> selling of patents to other companies.
>>> I do not see many of those displays for sale, none AFAIK.
>>> At high field strength (due to small sizes) you are asking for trouble,
>>> things will be ripped of the surface.
>>>
>>> And 460 GHz is not realy that fast, just a quick search with Bing:
>>> &#4294967295; Silicon-germanium (SiGe) transistor at 798 gigahertz (GHz) fMAX:
>>> &#4294967295;&#4294967295;
>>> http://www.news.gatech.edu/2014/02/17/silicon-germanium-chip-sets-new-speed-record
>>>
>>>
>>> NASA, they also have a prototype warp drive...
>>> sigh
>> 
>> Fun.&#4294967295; I knew John Cressler at IBM Watson--I took a BJT design course
>> from him back in about 1988, when IBM was still building mainframes out
>> of ECL.
>> 
>> Re: field emitters
>> 
>> Just in order to get an output power level above the Johnson noise of 50
>> ohms in a 460 GHz bandwidth, you need
>> 
>> Pout > -204 dBW + 10 log(460 GHz) = -87 dBW (2 nW).
>> 
>> 
>> The RMS current in 50 ohms is I = sqrt(50* 2nW) = 300 uA.
>
>Never mind.  Note to self: don't post before having coffee.
>
>Should be sqrt(2 nW/50) = 6 uA.
>
>> 
>> With a transconductance of 20 nS/um (quoted by the Pittsburgh guys in
>> Nature,
>> https://www.nature.com/nnano/journal/v7/n8/full/nnano.2012.107.html,
>> you'd need a device with gate width
>> 
>> W > 300 uA/(20 nA/um) = 15000 um (15 mm).
>
>W > 6 uA/(20 nA/V/um) = 300 um, assuming 1V worth of grid drive.  Of
>course that's with 1V of grid swing, so the voltage gain is about 0.0003
>(50 ohms times 6 uA / 1V).
>
>To get actual voltage gain, it would have to be much, much bigger.  To
>reach a voltage gain of 1.0 (20 mA plate current @ 1V grid drive) it
>would need to be
>
>W > 20 mA / (20 nA/um/V * 1 V) = 1,000,000 um = 1 meter wide, which is
>about 1500 wavelengths at 460 GHz.
>
>And that's not counting the capacitance, which for something that size
>would be in the tens of picofarads.
>
>So just getting a voltage gain of 1.0 in 50 ohms at 460 GHz would
>require quite the distributed amplifier structure, assuming you could
>keep the losses low enough even to get near there.
>
>Cheers
>
>Phil Hobbs


That would be cool, a row of emitter tips squirting electrons onto a
strip anode, a field-emitter distributed amplifier or, in a circle, an
oscillator.

I think someone patented a distributed thermionic triode, but I don't
know that it was ever used. There were CRTs with distributed
deflection plates. It's a neat concept.

https://www.dropbox.com/s/evoq6p2nvzyl6wo/547_crt.JPG?raw=1

https://www.dropbox.com/s/r6c3zkwlqrayt53/519_CRT.JPG?raw=1


A field emitter in a cavity might oscillate. Too bad they degrade so
fast.



-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics
Reply by Phil Hobbs ●November 4, 20172017-11-04
On 11/04/2017 10:58 AM, Phil Hobbs wrote:

> On 11/04/2017 03:56 AM, Jan Panteltje wrote:
>> On a sunny day (Fri, 3 Nov 2017 16:58:22 -0500) it happened "Tim
>> Williams"
>> <tmoranwms@gmail.com> wrote in <otiop9$chs$1@dont-email.me>:
>>
>>> "Steve Wilson" <no@spam.com> wrote in message
>>> news:XnsA822AB7D5D5F6idtokenpost@69.16.179.23...
>>>> What causes the erosion? Is it the high voltage used?
>>>>
>>>> I'm not trying to prove you wrong. I'm trying to understand what the
>>>> mechanism is in case it has any bearing on some of my other projects.
>>>>
>>>> As I stated earlier, I could find no reference to tip erosion except
>>>> that
>>>> caused by ion impact damage or operation at high voltage. There was
>>>> nothing
>>>> on tip erosion at low voltages.
>>>>
>>>
>>> What's the physics at work, anyway?
>>>
>>> One would suppose the required voltage is proportional to the binding
>>> energy
>>> and/or work function of the material, and so tungsten would be the best.
>>> But those are infinite and ideal properties.
>>>
>>> One needs to take into account the boundary conditions, which are quite
>>> significant in an atomic-scale point.&#4294967295; The band structure will be very
>>> different in that region (annular confinement modes, where the band
>>> splits
>>> into discrete levels spaced according to the dimensions of the tip?),
>>> and
>>> maybe that leads to weakening of the material (a zone of low electron
>>> density acting as a stress raiser?).&#4294967295; One would then suppose, there
>>> exists
>>> an ideal tip shape which maximizes its minimum binding energy, while
>>> minimizing the work function or electron tunneling probability.&#4294967295;
>>> Maybe it's
>>> a surface of rotation, with a funny curved profile; maybe it's not
>>> round,
>>> but polygonal; maybe it's a stepped cylinder, or pyramid or cone;
>>> maybe it's
>>> even hollow, or filled with other elements!
>>>
>>> Would be interesting to see some analysis of this ... but wouldn't be so
>>> interested as to dare attempt it myself. :-x
>>>
>>> Tim
>>
>> Some time ago there was some commotion about companies giving up on
>> field emission display tech,
>> selling of patents to other companies.
>> I do not see many of those displays for sale, none AFAIK.
>> At high field strength (due to small sizes) you are asking for trouble,
>> things will be ripped of the surface.
>>
>> And 460 GHz is not realy that fast, just a quick search with Bing:
>> &#4294967295; Silicon-germanium (SiGe) transistor at 798 gigahertz (GHz) fMAX:
>> &#4294967295;&#4294967295;
>> http://www.news.gatech.edu/2014/02/17/silicon-germanium-chip-sets-new-speed-record
>>
>>
>> NASA, they also have a prototype warp drive...
>> sigh
> 
> Fun.&#4294967295; I knew John Cressler at IBM Watson--I took a BJT design course
> from him back in about 1988, when IBM was still building mainframes out
> of ECL.
> 
> Re: field emitters
> 
> Just in order to get an output power level above the Johnson noise of 50
> ohms in a 460 GHz bandwidth, you need
> 
> Pout > -204 dBW + 10 log(460 GHz) = -87 dBW (2 nW).
> 
> 
> The RMS current in 50 ohms is I = sqrt(50* 2nW) = 300 uA.


Never mind.  Note to self: don't post before having coffee.

Should be sqrt(2 nW/50) = 6 uA.


> 
> With a transconductance of 20 nS/um (quoted by the Pittsburgh guys in
> Nature,
> https://www.nature.com/nnano/journal/v7/n8/full/nnano.2012.107.html,
> you'd need a device with gate width
> 
> W > 300 uA/(20 nA/um) = 15000 um (15 mm).


W > 6 uA/(20 nA/V/um) = 300 um, assuming 1V worth of grid drive.  Of
course that's with 1V of grid swing, so the voltage gain is about 0.0003
(50 ohms times 6 uA / 1V).

To get actual voltage gain, it would have to be much, much bigger.  To
reach a voltage gain of 1.0 (20 mA plate current @ 1V grid drive) it
would need to be

W > 20 mA / (20 nA/um/V * 1 V) = 1,000,000 um = 1 meter wide, which is
about 1500 wavelengths at 460 GHz.

And that's not counting the capacitance, which for something that size
would be in the tens of picofarads.

So just getting a voltage gain of 1.0 in 50 ohms at 460 GHz would
require quite the distributed amplifier structure, assuming you could
keep the losses low enough even to get near there.

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
Reply by Phil Hobbs ●November 4, 20172017-11-04
On 11/04/2017 03:56 AM, Jan Panteltje wrote:

> On a sunny day (Fri, 3 Nov 2017 16:58:22 -0500) it happened "Tim Williams"
> <tmoranwms@gmail.com> wrote in <otiop9$chs$1@dont-email.me>:
> 
>> "Steve Wilson" <no@spam.com> wrote in message
>> news:XnsA822AB7D5D5F6idtokenpost@69.16.179.23...
>>> What causes the erosion? Is it the high voltage used?
>>>
>>> I'm not trying to prove you wrong. I'm trying to understand what the
>>> mechanism is in case it has any bearing on some of my other projects.
>>>
>>> As I stated earlier, I could find no reference to tip erosion except that
>>> caused by ion impact damage or operation at high voltage. There was
>>> nothing
>>> on tip erosion at low voltages.
>>>
>>
>> What's the physics at work, anyway?
>>
>> One would suppose the required voltage is proportional to the binding energy
>> and/or work function of the material, and so tungsten would be the best.
>> But those are infinite and ideal properties.
>>
>> One needs to take into account the boundary conditions, which are quite
>> significant in an atomic-scale point.  The band structure will be very
>> different in that region (annular confinement modes, where the band splits
>> into discrete levels spaced according to the dimensions of the tip?), and
>> maybe that leads to weakening of the material (a zone of low electron
>> density acting as a stress raiser?).  One would then suppose, there exists
>> an ideal tip shape which maximizes its minimum binding energy, while
>> minimizing the work function or electron tunneling probability.  Maybe it's
>> a surface of rotation, with a funny curved profile; maybe it's not round,
>> but polygonal; maybe it's a stepped cylinder, or pyramid or cone; maybe it's
>> even hollow, or filled with other elements!
>>
>> Would be interesting to see some analysis of this ... but wouldn't be so
>> interested as to dare attempt it myself. :-x
>>
>> Tim
> 
> Some time ago there was some commotion about companies giving up on field emission display tech,
> selling of patents to other companies.
> I do not see many of those displays for sale, none AFAIK.
> At high field strength (due to small sizes) you are asking for trouble,
> things will be ripped of the surface.
> 
> And 460 GHz is not realy that fast, just a quick search with Bing:
>   Silicon-germanium (SiGe) transistor at 798 gigahertz (GHz) fMAX:
>    http://www.news.gatech.edu/2014/02/17/silicon-germanium-chip-sets-new-speed-record
> 
> NASA, they also have a prototype warp drive...
> sigh


Fun.  I knew John Cressler at IBM Watson--I took a BJT design course 
from him back in about 1988, when IBM was still building mainframes out 
of ECL.

Re: field emitters

Just in order to get an output power level above the Johnson noise of 50 
ohms in a 460 GHz bandwidth, you need

Pout > -204 dBW + 10 log(460 GHz) = -87 dBW (2 nW).


The RMS current in 50 ohms is I = sqrt(50* 2nW) = 300 uA.

With a transconductance of 20 nS/um (quoted by the Pittsburgh guys in 
Nature,
https://www.nature.com/nnano/journal/v7/n8/full/nnano.2012.107.html, 
you'd need a device with gate width

W > 300 uA/(20 nA/um) = 15000 um (15 mm).

IOW it's the size of a 12AX7A except flatter--just to get out of the 
Johnson noise.

Not what you'd call a super practical device.

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
Reply by Jan Panteltje ●November 4, 20172017-11-04
On a sunny day (Fri, 3 Nov 2017 16:58:22 -0500) it happened "Tim Williams"
<tmoranwms@gmail.com> wrote in <otiop9$chs$1@dont-email.me>:


>"Steve Wilson" <no@spam.com> wrote in message 
>news:XnsA822AB7D5D5F6idtokenpost@69.16.179.23...
>> What causes the erosion? Is it the high voltage used?
>>
>> I'm not trying to prove you wrong. I'm trying to understand what the
>> mechanism is in case it has any bearing on some of my other projects.
>>
>> As I stated earlier, I could find no reference to tip erosion except that
>> caused by ion impact damage or operation at high voltage. There was 
>> nothing
>> on tip erosion at low voltages.
>>
>
>What's the physics at work, anyway?
>
>One would suppose the required voltage is proportional to the binding energy 
>and/or work function of the material, and so tungsten would be the best. 
>But those are infinite and ideal properties.
>
>One needs to take into account the boundary conditions, which are quite 
>significant in an atomic-scale point.  The band structure will be very 
>different in that region (annular confinement modes, where the band splits 
>into discrete levels spaced according to the dimensions of the tip?), and 
>maybe that leads to weakening of the material (a zone of low electron 
>density acting as a stress raiser?).  One would then suppose, there exists 
>an ideal tip shape which maximizes its minimum binding energy, while 
>minimizing the work function or electron tunneling probability.  Maybe it's 
>a surface of rotation, with a funny curved profile; maybe it's not round, 
>but polygonal; maybe it's a stepped cylinder, or pyramid or cone; maybe it's 
>even hollow, or filled with other elements!
>
>Would be interesting to see some analysis of this ... but wouldn't be so 
>interested as to dare attempt it myself. :-x
>
>Tim


Some time ago there was some commotion about companies giving up on field emission display tech,
selling of patents to other companies.
I do not see many of those displays for sale, none AFAIK.
At high field strength (due to small sizes) you are asking for trouble,
things will be ripped of the surface.

And 460 GHz is not realy that fast, just a quick search with Bing:
 Silicon-germanium (SiGe) transistor at 798 gigahertz (GHz) fMAX:
  http://www.news.gatech.edu/2014/02/17/silicon-germanium-chip-sets-new-speed-record

NASA, they also have a prototype warp drive...
sigh
Reply by Steve Wilson ●November 3, 20172017-11-03
Steve Wilson <no@spam.com> wrote:


> John Larkin <jjlarkin@highlandtechnology.com> wrote:

 

>> On Fri, 03 Nov 2017 15:30:54 GMT, Steve Wilson <no@spam.com> wrote:

  

>>>John Larkin <jjlarkin@highlandtechnology.com> wrote:

 

>>>> What all these things have in common is that the emitting tip erodes.
>>>> In the atom probe, that's a feature. In the other cases, it's a
>>>> fatality. 

 

>>>What causes erosion in a device running at 10 volts when there is no 
>>>ionization impact? 

  

>> The same thing that has ruined every other field-effect emitter for
>> the last 40 years or so? 

 

> What causes the erosion? Is it the high voltage used?

 

> I'm not trying to prove you wrong. I'm trying to understand what the 
> mechanism is in case it has any bearing on some of my other projects.

 

> As I stated earlier, I could find no reference to tip erosion except
> that caused by ion impact damage or operation at high voltage. There was
> nothing on tip erosion at low voltages.

 
No response to my request. This means you have no information on tip 
erosion at low voltages.

This is good news. Thanks.
Reply by Steve Wilson ●November 3, 20172017-11-03
"Tim Williams" <tmoranwms@gmail.com> wrote:


> "Steve Wilson" <no@spam.com> wrote in message 
> news:XnsA822AB7D5D5F6idtokenpost@69.16.179.23...
>> What causes the erosion? Is it the high voltage used?



>> I'm not trying to prove you wrong. I'm trying to understand what the
>> mechanism is in case it has any bearing on some of my other projects.



>> As I stated earlier, I could find no reference to tip erosion except
>> that caused by ion impact damage or operation at high voltage. There
>> was nothing on tip erosion at low voltages.



> What's the physics at work, anyway?

 

> One would suppose the required voltage is proportional to the binding
> energy and/or work function of the material, and so tungsten would be
> the best. But those are infinite and ideal properties.

 

> One needs to take into account the boundary conditions, which are quite 
> significant in an atomic-scale point.  The band structure will be very 
> different in that region (annular confinement modes, where the band
> splits into discrete levels spaced according to the dimensions of the
> tip?), and maybe that leads to weakening of the material (a zone of low
> electron density acting as a stress raiser?).  One would then suppose,
> there exists an ideal tip shape which maximizes its minimum binding
> energy, while minimizing the work function or electron tunneling
> probability.  Maybe it's a surface of rotation, with a funny curved
> profile; maybe it's not round, but polygonal; maybe it's a stepped
> cylinder, or pyramid or cone; maybe it's even hollow, or filled with
> other elements! 

 

> Would be interesting to see some analysis of this ... but wouldn't be so
> interested as to dare attempt it myself. :-x

 

> Tim


Wikipedia has a long article on field emission:

https://en.wikipedia.org/wiki/Field_electron_emission

It does not discuss tip erosion. A few articles I found say the electric 
field exceeds the binding energy of the atom, so it separates from the tip.

This means that high voltage and a sharp tip are needed. This has been my 
biggest problem from the beginning, since I thought I needed high voltage 
for electron emission, but I worried it would cause tip erosion and ozone 
generation. However, if I can get sufficient electron emission at low 
voltage as described in the IEEE article, that should reduce tip erosion 
and ozone generation. I'm going to give it a try.
Reply by Tim Williams ●November 3, 20172017-11-03
"Steve Wilson" <no@spam.com> wrote in message 
news:XnsA822AB7D5D5F6idtokenpost@69.16.179.23...

> What causes the erosion? Is it the high voltage used?
>
> I'm not trying to prove you wrong. I'm trying to understand what the
> mechanism is in case it has any bearing on some of my other projects.
>
> As I stated earlier, I could find no reference to tip erosion except that
> caused by ion impact damage or operation at high voltage. There was 
> nothing
> on tip erosion at low voltages.
>


What's the physics at work, anyway?

One would suppose the required voltage is proportional to the binding energy 
and/or work function of the material, and so tungsten would be the best. 
But those are infinite and ideal properties.

One needs to take into account the boundary conditions, which are quite 
significant in an atomic-scale point.  The band structure will be very 
different in that region (annular confinement modes, where the band splits 
into discrete levels spaced according to the dimensions of the tip?), and 
maybe that leads to weakening of the material (a zone of low electron 
density acting as a stress raiser?).  One would then suppose, there exists 
an ideal tip shape which maximizes its minimum binding energy, while 
minimizing the work function or electron tunneling probability.  Maybe it's 
a surface of rotation, with a funny curved profile; maybe it's not round, 
but polygonal; maybe it's a stepped cylinder, or pyramid or cone; maybe it's 
even hollow, or filled with other elements!

Would be interesting to see some analysis of this ... but wouldn't be so 
interested as to dare attempt it myself. :-x

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: https://www.seventransistorlabs.com/