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Behind the Scenes At a Quantum Dot Factory

Posted by Soulskill on from the harvesting-the-dot-crop dept.

Tekla Perry writes: In a nondescript office complex in Milpitas, Calif., Nanosys is making enough quantum dots to populate 6 million 60-inch television screens annually. "The process goes on in what looks like a microbrewery. In about half a dozen large metal tanks ... Nanosys combines cadmium and selenium and adjusts the temperature, concentration, and catalysts added to force these precursors to combine into stable crystals of cadmium selenide. Then, by readjusting the conditions, the system stops the formation of crystals and triggers the beginning of crystal growth. A computer controls the process according to a programmed “recipe;” staff members monitor the growth of the crystals by shining light on them and measuring the wavelength of the fluorescence; the smallest crystals don’t fluoresce at all, then, as the crystals get larger, the wavelength changes. Nanosys stops the process when the fluoresced light hits the target wavelength, which varies depending on what particular display industry standard that the batch of film is designed to meet."

37 comments

  1. Quantum Dot? by chinton · · Score: 2

    Isn't that what got you into the secret room in Adventure?

    1. Re:Quantum Dot? by TWX · · Score: 2

      An expalanation of what a quantum dot is would have been nice.

      --
      Do not look into laser with remaining eye.
    2. Re:Quantum Dot? by Thud457 · · Score: 4, Funny

      They're like Quantum Crows, but are fruit-flavored instead of licorice.

      --

      the preceding comment is my own and in no way reflects the opinion of the Joint Chiefs of Staff

    3. Re:Quantum Dot? by bws111 · · Score: 2

      According to TFA, they are nanoscale semiconductor crystals that turn blue light into narrow-spectrum greens and reds.

    4. Re:Quantum Dot? by Livius · · Score: 1

      I believe the use of 'quantum' is to sound high-tech and futuristic. Except of course to anyone who knows even the rudiments of quantum theory.

    5. Re:Quantum Dot? by Anonymous Coward · · Score: 0

      Like the bit in the article that has a URL to this? '(More on how that works here.)" http://spectrum.ieee.org/tech-talk/consumer-electronics/audiovideo/what-the-heck-are-quantum-dots

    6. Re:Quantum Dot? by Anonymous Coward · · Score: 0

      An expalanation of what a quantum dot is would have been nice.

      The ones I worked with on my Phd (Indium Arsenide, mainly) are grown by Stranski-Krastranow growth, which is where you grow layers of semiconductor on top of each other using Molecular beam epitaxy, the lattices dont match properly and the QD layer "puckers" up into small nodules which have a size thats small enough to create a "box" where the quantum energy levels inside the dot are discrete, kind of like the example problems you get in basic quantum mechanics, there are similar materials that confine electrons in only 2D (Quantum Wells), 1D (Quantum Wires), and 0D(Quantum Dots), it is just referrring to how many physical degrees of freedom the electrons have to move in a classical non quantum way. At least when I did my research the main interest was in looking into room temperature lasers and optical devices particularly in the blue range. The good thing is you can choose the material (in theory) and "engineer" the spacing and depth of the quantum energy levels inside the dot so that they capture electrons from the continuum above the energy band gap, these "fall into" the dot, and now you have lots of confined electrons that you can stimulate to transition between energy levels cohesively (the basis for lasers), and the gap between the resting energy level and the continuum outside the dot has to be large enough to be greater than "thermal energy of the electrons at room temperature", otherwise the electrons just escape. I did my work at the university of sheffield in the mid to late 90s (Harris), not hard to find.

    7. Re:Quantum Dot? by Anonymous Coward · · Score: 0

      They are semiconductors with custom bandgaps allowing for excitations that emit photons centered around a desired wavelength. The applicability of "quantum" in their name should be straightforward for anyone with a background in quantum mechanics, or even basic chemistry, and who knows what a quantum dot is.

  2. Disposal problem? by Anonymous Coward · · Score: 0

    That is a lot of cadmium entering the environment...but we never think about that stuff beforehand...

    1. Re:Disposal problem? by bws111 · · Score: 1

      TFA discusses this, and they are working on cadmium-free dots, but they are harder to produce. They use indium and phosphorus for those.

    2. Re:Disposal problem? by Y.A.A.P. · · Score: 2

      TFA discusses this, and they are working on cadmium-free dots, but they are harder to produce. They use indium and phosphorus for those.

      Yes. The article also continues to further explain that the cadmium-free dots are less efficient, which makes them less-desirable to the display manufacturers.

      Also, to GP, the CEO of the profiled company notes in the article that they do not release any Cadmium in the production of the quantum dots, but they have no control over how the displays are disposed of when they are no longer wanted. Considering the environmental consciousness that they are stated to show, I'm sure the company would love to get those dumped displays and get that Cadmium back, rather than letting it being lost in the environment.

    3. Re:Disposal problem? by rogoshen1 · · Score: 4, Funny

      that's racist. please use "native americium" going forward.

    4. Re: Disposal problem? by smaddox · · Score: 1

      It's pretty stable in salt form---much less of a problem than elemental Cd from batteries or Hg from florescent lights. Also, it's pretty well encapsulated in the TVs.

    5. Re:Disposal problem? by Anonymous Coward · · Score: 0

      TFA discusses this, and they are working on cadmium-free dots, but they are harder to produce. They use indium and phosphorus for those.

      Yes. The article also continues to further explain that the cadmium-free dots are less efficient, which makes them less-desirable to the display manufacturers.

      Also, to GP, the CEO of the profiled company notes in the article that they do not release any Cadmium in the production of the quantum dots, but they have no control over how the displays are disposed of when they are no longer wanted. Considering the environmental consciousness that they are stated to show, I'm sure the company would love to get those dumped displays and get that Cadmium back, rather than letting it being lost in the environment.

      Cadmium is not a Proper Noun you Fuck-ass.

  3. Thank you, Tekla Perry! by Y.A.A.P. · · Score: 3, Interesting

    I have been reading /. for far longer than my ID # indicates. IIRC, it was 1999 when I happened upon the site, I just didn't bother to join, because I never had anything useful to say. Back then it was "News for Nerds, Stuff that Matters." Unfortunately, that guiding mantra no longer adorns the /. bannerhead and we are poorer for it.

    This submission is a perfect example of "News for Nerds, Stuff that Matters." The summary doesn't tell you everything, you have to click through and read the article to get the true value of it. I read the article and it was very informative. I learned interesting information from it. It wasn't just interesting, I might actually use that information in the future.

    Thank you for perking up my day with interesting information and giving me hope that /. will continue to be a site to return to for quality information and news.

    1. Re:Thank you, Tekla Perry! by Anonymous Coward · · Score: 0

      /. has ceased to be a site worth going to when it developed it's code ceaselessy but yet remains stuck in the 1990s. There is no red envelope or similiar notifications button, to see replies at a glance. No way to even find old comments that slip off the relatively short comment list except through google and chance. And no way for a guest to adjust comment levels and such for viewing on an ipad or iphone (other mobile?) unless they sign in -- the one thing from the 1990s that was good and adequate, was done away by default by these sliding scales that add nothing.

      Reddit used to suck because of comment quality. Many subreddits fixed that in the meantime. And now /. is on the long decline. The only place reddit really sucks at is threading for good comments in a multihundred/thousand commented story -- routinely relevant comments get lost in sheer noise and idiocy with upvotes while /. has that problem much less.

    2. Re:Thank you, Tekla Perry! by Anonymous Coward · · Score: 0

      Most of Slashdot's content is just regurgitated fluff that has risen to the top of Reddit.com.

    3. Re:Thank you, Tekla Perry! by tepples · · Score: 2

      There is no red envelope or similiar notifications button, to see replies at a glance

      Click the word "Slashdot" at the top left of each page to go to the home page, and your replies should be just below your username in a box at the top of the right column.

      No way to even find old comments that slip off the relatively short comment list

      I get a "Load More Comments" button at the bottom.

    4. Re:Thank you, Tekla Perry! by Anonymous Coward · · Score: 0

      May I suggest you simply start reading IEEE's Spectrum (the source of this article)? They consistently publish high quality well researched articles.

  4. BE part of the SOLUTION. by Thud457 · · Score: 3, Informative

    The button to Submit a story is right in front of your nose a the top of the page.
    Unless you're implying the editurs are idiots and ignore perfectly nerdulent story suggestions.

    --

    the preceding comment is my own and in no way reflects the opinion of the Joint Chiefs of Staff

    1. Re:BE part of the SOLUTION. by Lunix+Nutcase · · Score: 0

      Unless you're implying the editurs are idiots

      No need to imply anything. That's already long-established fact.

    2. Re:BE part of the SOLUTION. by Anonymous Coward · · Score: 0

      Unless you're implying the editurs are idiots and ignore perfectly nerdulent story suggestions.

      I will.

      I have submitted plenty of nerdy stories and none have made it.

      What does make it?

      Anything that will bring clicks. Anything that will get you dorks in an uproar will make it.

      Occasionally, real geeky stuff is thrown in on slow days, but it looks like those articles are submitted on those days.

      EDITOR1: "Shit! We don't have enough for today!"

      EDITR2: "Hey, here's a sciency article that's looks like it's geeky. Let's post it!"

      EDITOR1:"Yeah! Good."

    3. Re:BE part of the SOLUTION. by Y.A.A.P. · · Score: 1

      The button to Submit a story is right in front of your nose a the top of the page.
          Unless you're implying the editurs are idiots and ignore perfectly nerdulent story suggestions.

      You are correct, sir, in that I have not done my part in keeping /. as it was, can, and should be. I implied nothing about the current editorial staff, nor did I wish to do so, regardless of my views on such matters in private. I would like to live up to my own perceived responsibilities as a member of the /. community. Based on my past history, however, that is unlikely to happen. I will, however, keep the thought of making such contributions closer to the fore, thanks to your comment. I can only hope that others take similar encouragement.

  5. Sorry, but story is BS by Anonymous Coward · · Score: 0

    I tried to go to quantum.factory, but it didn't resolve.

    I don't even think .factory is a valid TLD. But these days you never know.

    1. Re:Sorry, but story is BS by quantumghost · · Score: 1

      I went to a quantum factory, but since it wasn't moving, I couldn't find it. *sigh*.

    2. Re:Sorry, but story is BS by Anonymous Coward · · Score: 0

      In the novel of "A Scanner Darkly", they have a drug-fuelled discussion about trying to find a microdot factory in a seemingly empty lot, IIRC.

  6. How big is it? by AnotherBlackHat · · Score: 1

    Anyone know what the maximum size of a quantum dot is?
    Could they make ones that emit microwaves, or even radio?

    1. Re:How big is it? by inqrorken · · Score: 4, Informative

      A few tens of nanometers in diameter. Dots emit light at (more or less) a single frequency (it's actually Gaussian around the chosen frequency.) To emit that photon, the dot has to absorb a photon of higher energy. Since right now dots are absorbing visible, it's energetically possible to emit in microwave or radio frequencies. While I believe it's possible to do so, existing methods may be more efficient (energy-wise or cost-wise), or we may not have discovered dot materials that allow for those emission frequencies.

    2. Re: How big is it? by smaddox · · Score: 2

      Short answer is no. Although there are plenty of other semiconductor devices that can operate in the microwave.

      The "quantum" part of quantum dots is that the effective bandgap of the semiconductor, which controls the wavelength of luminescence, is increased by quantum confinement. Google particle in a box for more information.

    3. Re:How big is it? by Anonymous Coward · · Score: 0

      For the last time...

      It's not how big it is, it's how you use it.

  7. Toxic chemicals in 'office complex'? by Anonymous Coward · · Score: 1

    Both cadmium and selenium are toxic. Cadmium has been considered as an environment pollutant

    I simply can't imagine someone setting up a factory which uses cadmium and selenium in an area described as a 'nondescript office complex'

    How do they get the green light from EPA in the first place?

    1. Re:Toxic chemicals in 'office complex'? by kanweg · · Score: 2

      "How do they get the green light from EPA in the first place?"

      By shining blue light on green quantum dots, I guess.

      Bert

    2. Re:Toxic chemicals in 'office complex'? by Anonymous Coward · · Score: 0

      I simply can't imagine someone setting up a factory which uses cadmium and selenium in an area described as a 'nondescript office complex',

      Why? What makes it any more difficult to clean up a spill of cadmium or selenium in an office park than any other location, especially considering they would be a smaller scale use? It is not like either one produces fumes. As long as they are not illegally dumping waste products from their process, it is rather easy to contain such materials.

    3. Re:Toxic chemicals in 'office complex'? by Anonymous Coward · · Score: 0

      Nanoco in the UK makes quantum dots that are cadmium-free at all stages of the manufacturing process. Dow have licensed their technology and are building a full-scale QD plant (hopefully the first of many) in south Korea that will come on line mid 2015, producing for the LCD display market (TVs, pads, phones).

      Nanoco are also developing QDs suitable for the lighting and medical imaging markets, amongst others.

  8. Man I feel dumb by Anonymous Coward · · Score: 0

    I can't even understand what the article is about from the summary :( Giving up my mod points with my geek card...

  9. Republic of India by tepples · · Score: 1

    I can think of roughly 1.25 billion people who don't find "Indian" racist.