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A book for Rick M

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Posted on May 23, 2011 at 13:19:18
unclestu
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 Slightly older (1993) but quite interesting: Will McCarthy's Hacking Matter. Its subtitles levitating chairs, quantum mirages and the infinite weirdness of programmable atoms. I always thought quantum dots were a marketing catchword but apparently ( my bad)there really are such critters.

But lo and behold, they are simply PNP sandwiches sized appropriately sized.The quantum wells are now commonly found in those laser pointers.

I'm sure you have already dealt with such objects, but it was interesting for me.

Stu

 

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Oh, goodie, quantum dots! Now, we're getting somewhere. nt, posted on May 23, 2011 at 16:25:36
geoffkait
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 nt

 

RE: Oh, goodie, quantum dots! Now, we're getting somewhere. nt, posted on May 24, 2011 at 14:46:22
6bq5
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 I actually worked hard for about six years manufacturing quantum dots(r) for use as flurophores in biological assays. The Company was Quantum Dot Corp., based in Hayward, CA and we offered six different emission spectra, 525, 565, 585, 605, 655 and 705nM emission. They were quite consistent - the ones we shipped to customers with a full width at Half-Max of 30 nM.
Unfortunately the process did not survive the move to Oregon, after the new Owners acquired the company, and not much is left - but they were fun to work with...

 

RE: Oh, goodie, quantum dots! Now, we're getting somewhere. nt, posted on May 25, 2011 at 05:59:28
geoffkait
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 I've always wondered, do quantum dots have to be assembled in the dark? If so, how can you see what you're doing? Do you have to wear infrared googles? :-)

 

RE: Oh, goodie, quantum dots! Now, we're getting somewhere. nt, posted on May 25, 2011 at 12:12:19
6bq5
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 The 'dots' that I worked on making were Cadmium-Selanide, or CdSe with a Zinc Sulfide outer shell - none of the synthesis was done in the dark, and they did NOT photo bleach. The 655 dots were so efficient, that in large bottles of dots at high concentrations, they would be opaque, as then were absorbing so much of the light present.
What was requires were Air-free apparatus, and the synthesis was performed in a solvent at 300 degrees C. There were some fireworks with the original methods, as we were injecting dimethylcadmium into the hot solvent with dissolved selenium...A chemists' dream of lots of cool equipment and volatile chemicals...

 

RE: Oh, goodie, quantum dots! Now, we're getting somewhere. nt, posted on May 27, 2011 at 09:59:16
geoffkait
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 I am working feverishly on the next generation intelligent chip, which will also be an edge emitter.

 

RE: quantum dots, posted on May 27, 2011 at 12:59:24
unclestu
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 The book makes a difference between quantum wells, quantum wires and quantum dots.

The wires and dots can emit various spectra, with the wells being utilized for most of the commercial laser pointers we see on the market where by visible light is emitted from the top layer of the PNP junction. The Quantum wire can emit much more powerful spectra, well beyond the visible spectra and the spectra is emitted from the center portion of the PNP wafer, The N portion of the wafer The dots can be made small enough to involve de Broglie wavelength energy from the electrons captured in the wafer but my guess is that they could be made large enough to emit visible light. However, the author makes the distinction that the dots have the N layer holding the electrons and the P layer sandwich creating the boundaries for those electrons.

The wavelengths you mention seem to span the visible yellow to red spectra. It's amazing the tightness with which you could tune those frequencies. The doping necessary to fabricate them must have been incredibly small but even, in order to achieve that kind of commercial QC.

Stu

 

RE: A book for Rick M, posted on May 27, 2011 at 15:21:55
rick_m
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 Ok...

I googled your title and downloaded the almost free multimedia version. He wants a buck and I'll send him one if I can make any sense of it. Unfortunately for him it's probably a lost cause...

You certainly have an eclectic taste in books Stu!

Thanks, Rick

 

RE: Oh, goodie, quantum dots! Now, we're getting somewhere. nt, posted on May 27, 2011 at 15:37:48
rick_m
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 "Unfortunately the process did not survive the move to Oregon"

Off the wall question: Were they in Eugene by any chance?

Idle curiosity...

Rick

 

RE: A book for Rick M, posted on May 27, 2011 at 15:54:41
unclestu
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 Kinda older book but very succinct data. He's chief technology officer for the Galileo Institute, and he is a very hands on type of guy: even gives his patent on the use of quantum dots at the tail end of the book. Thing I like about it is that he strips away a lot of the mystery when reading about the Quantum "this and that". They are all basically a PNP transistor, and I'm definitely sure you know way more about that application than I do!


Stu

 

RE: A book for Rick M, posted on May 28, 2011 at 13:44:51
rick_m
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 What a fascinating read! I'm about half done and am giving my aging eyes and brain a break. Glad that you saw fit to bring it up.

The device topology may be PNPish but the application is way different. Hey, they bias it 'wrong', no wonder they are having problems with stored charge... Well I've always regarded it as a problem!

Since the whole business seems rather exotic to me I'm glad that while the author appears knowledgeable that he is clearly more interested in providing a good ol' arm-waving explanation than trying to impress us with his erudition.

Regards, Rick


 

RE: quantum dots, posted on May 29, 2011 at 03:17:42
geoffkait
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 "The book makes a difference between quantum wells, quantum wires and quantum dots. The wires and dots can emit various spectra, with the wells being utilized for most of the commercial laser pointers we see on the market where by visible light is emitted from the top layer of the PNP junction."

And, getting a little closer to home, wells are utilized for lasers in CD players where invisible infrared light is emitted. And for lasers in DVD players where visible red light is emitted.

"The Quantum wire can emit much more powerful spectra, well beyond the visible spectra and the spectra is emitted from the center portion of the PNP wafer, The N portion of the wafer

So what? Quantum dots can be designed to emit beyond the visible spectrum, too. That's why they're called "programmable matter."

"The dots can be made small enough to involve de Broglie wavelength energy from the electrons captured in the wafer but my guess is that they could be made large enough to emit visible light."

The dots exist ONLY because of the de Broglie wavelength. I.e., the dots can ONLY be made very small, that's the whole point. And, even though they're very small, the dots can be made to emit visible light. Why do you think bottles of dots are red, green, blue, etc.?

 

Bottles of dots?, posted on May 29, 2011 at 07:55:16
rick_m
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 So you can buy these things off the shelf?

I knew that you used them and was thinking of inquiring of you what the design/Fab process is like. These creatures are new to me, shoot I'm actually from the tube era (but I outgrew them)...

Rick

 

RE: Bottles of dots?, posted on May 29, 2011 at 08:03:52
geoffkait
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 Heck, I'm just going by what the guy said to me below, you know, about the 655 bottle being opaque...

 

RE: Bottles of dots?, posted on May 29, 2011 at 12:17:45
rick_m
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 OK.

But even though I've finished the paper, I still don't understand even though i is now an exspurt...

Why would a jar of 655 dots be opaque? It seems to me that if they were excited they'd be red, if they were absorbing red they'd look green.

Maybe I should stick to parts potted in epoxy...

Rick

 

RE: A book for Rick M, posted on May 29, 2011 at 12:36:39
rick_m
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 Thanks again Stu, I greatly enjoyed the first half but started skimming when he entered his science fiction writer mode and lapsed into speculative fiction. I noticed that his web site has been abandoned so I suspect that the speculation tuned out to be idle indeed...

But if somehow, whatever these things do, they turn out to be useful for "social networking" then I am sure there is a fortune to be made!

Rick

 

RE: Bottles of dots?, posted on May 29, 2011 at 12:59:45
geoffkait
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 Not sure I understand your question. If the bottle were red wouldn't that be opaque?

 

RE: Bottles of dots?, posted on May 29, 2011 at 14:02:40
rick_m
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 "If the bottle were red wouldn't that be opaque?"

I think opaqueness is more of a passive quality!

Rick

 

RE: Bottles of dots?, posted on May 29, 2011 at 14:09:35
geoffkait
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Looks opaque to me.

 

RE: Oh, goodie, quantum dots! Now, we're getting somewhere. nt, posted on May 31, 2011 at 12:01:29
6bq5
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 Yes - Eugene, Qdots(r) was purchased by Invitrogen, and Moved to the Molecular Probes site in Eugene.

 

RE: Bottles of dots?, posted on May 31, 2011 at 12:26:01
6bq5
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 The fabrication that we supported were done a relatively small scale; however at 8-12 nanometers in diameter, the dots themselves were even smaller. The 'bluer' the emission the smaller the diameter. To excite the dots,you need a light that is 'bluer' than the dot's emission. A Red(~600nM)Laser could not excite a 525 nM emitting Q-dot(r); however a Violet (405nM)laser could excite all the colors that we produced.
The 'tuning' of the color was actually a function of the time that the reaction was allowed to run - the 525nM dots 'nucleated' in under 30 seconds, and the 655 dots took ~10 minutes. Most of the visible spectra could be synthesized from Cadmium-Selanide materials, and we added tellurium to go into the infrared. We allso added a Zinc-Sulfide outer layer to 'passivate' the structure - making it more stable, and less prone to oxidization. These materials up to this point in the fabrication we Hydrophobic.
There are other metals in this region of the periodic table that theoretically should/could work; however there were a number of practical constraints. Most of the impediments came from what we called 'Lattice Miss-Match' where the structure of the atoms in the 'core' of the dot would not always form spheres, and did not provide a surface for the passivation layer to bond to the entire surface. The other issue that came up was the toxicity of the metals and the formats that the metals were available in(metal salts, and pyrophoric versions- diethylzinc...).

As to the opacity - the 655 nM materials were so efficient at being band-gap generators, that they would absorb most of the available light, additionally these were VERY concentrated solutions - we measured these in Molar units, not be volume or mass...Some of the bottles, were 500mL size, and we had LOTS of them.

 

RE: Oh, goodie, quantum dots! Now, we're getting somewhere. nt, posted on May 31, 2011 at 19:13:35
rick_m
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 Thanks!

Used to work just down the hill from them. Small world...

Rick

 

RE: Bottles of dots?, posted on June 1, 2011 at 03:39:15
geoffkait
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Inside the original GSIC-30 Intelligent Chip are 3 tiny silver discs embedded in a green plastic sheet. One skeptical customer went so far as to lug his GSIC-30 to a metallurgy lab to look for the alleged quantum material in the tiny silver discs with an electron microscope. The electron microscope did not find "artificial atoms" but it did identify Niobium (Nb) and Nickel (Ni) in the top surfaces of the metal discs and Copper (Cu), Zinc (Zn) and Aluminum (Al) in the bottom surfaces. The skeptical customer announced proudly, "No quantum material was found!" But what he and the folks at the lab didn't realize is that the "quantum material" is actually sandwiched between the metal layers and not visible to the microscope and that the particular metals identified by the microscope are highly reflective for the IR spectrum, thus contain, intensify and extend the photon chain emission of the dots.

 

Glad you find , posted on June 1, 2011 at 12:30:27
unclestu
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 it interesting. I know I did: yeah a bit far out sometimes, but it gives a good basic explanation stripping away the mystery of "quantum".

Stu

 

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