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Molybdenite As an Alternative To Silicon 169

Posted by timothy
from the mind-the-gap-sir dept.
An anonymous reader writes "Molybdenite (MoS2) can be used to make transistors that consume 100,000 times less energy in standby state. This mineral, which is abundant in nature, is often used as an element in steel alloys or as an additive in lubricants. Research carried out in Switzerland at the Ecole Polytechnique Fédérale de Lausanne's Laboratory of Nanoscale Electronics and Structures (LANES) has revealed that is a very effective semiconductor. Molybdenite's 1.8 electron-volt gap is ideal for transistors and gives it an advantage over graphene (which does not have a gap)."
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Molybdenite As an Alternative To Silicon

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  • Molykote? (Score:4, Interesting)

    by cvtan (752695) on Monday January 31, 2011 @12:13AM (#35053330)
    Isn't this just Moly disulphide, the lubricant in Molykote? http://www.dowcorning.com/content/molykote/anniversary.aspx?bhcp=1 [dowcorning.com]
    • by macraig (621737)

      Already asked and answered in TFS. What's your point, aside from giving Dow free advertising?

      • by Phoghat (1288088)
        He get's a $5 bonus every time he plugs a product on the interwebs
    • Re:Molykote? (Score:4, Informative)

      by pwagland (472537) on Monday January 31, 2011 @12:34AM (#35053434) Journal

      Isn't this just Moly disulphide, the lubricant in Molykote? http://www.dowcorning.com/content/molykote/anniversary.aspx?bhcp=1 [dowcorning.com]

      Possibly, from the article:

      This mineral, which is abundant in nature, is often used as an element in steel alloys or as an additive in lubricants. But it had not yet been extensively studied for use in electronics.

      That is this material has been known about for quite some time, however it's applications to electronics are only now being investigated, and he initial results appear to be quite favourable.

    • by Mr Z (6791)
      According to Wikipedia, Molybdenite is the mineral form of molybdenum disulphide. [wikimedia.org]
    • by c0lo (1497653)
      Yes, it is. The good news: unlike silicone, you can buy some of it and make your own transistors... errr... isn't it?
      • Re:Molykote? (Score:5, Interesting)

        by arivanov (12034) on Monday January 31, 2011 @03:05AM (#35054082) Homepage

        Probably not pure enough.

        You need 99.995+% purity for most semiconductor stuff (99.999+ for CPUs and memory) which can be achieved only via zone smelting. In order to zone smelt the material needs to be able to re-crystalize after being heated locally in the first place. If it does not you can forget using it as a production semiconductor. There are in fact plenty of materials out there which have electron gaps are more "interesting" than silicon. We just have not figured out how to grow to purify them in quantity.

        As far as MoS2 is concerned it does not melt and does not recrystalize (it decomposes straight away) so zone smelting is not an option. It decomposes straight away. So frankly I do not see how you can achieve 99.99+ purity to do anything useful with it.

        • by c0lo (1497653)

          So frankly I do not see how you can achieve 99.99+ purity to do anything useful with it.

          My bad: next time I'll explicitly put a *wink*.

        • Could we not try vapour phase deposition? I dunno, I've not looked at the numbers but I think that may help if we cannot zone refine. Alternatively for a thin layer you could lay it down by sputtering a coat on with a mass spectrograph to precisely select the ions you wanted - slow and doesnt make a very thick layer but that seems to be a bonus from what I read..
    • by adamchou (993073)
      so... what you're saying is my motherboard can now double as lube...
    • by RichiH (749257)

      Yes, it is.

      MoS_2 is pure awesome in any lubricant. Once you realize that this stuff has been known for about a hundred years, the mind boggles a little bit.

  • by RichMan (8097) on Monday January 31, 2011 @12:18AM (#35053344)

    In the latest technologies a lot of current is wasted to subthreshold conduction [wikipedia.org]. Current that flows then the transistors should be "off".

    A material with a higher bandgap 1.8ev to silicons 1.1ev will naturally have less leakage. As it is an exponential thing the leakage should not just be a reduction of 1.1 to 1.8 thing but much more significant.

    • Sounds promising:

      Advantages:

      • Higher melting point than silicon
      • Low thermal expansion
      • Low leakage
      • Allows extremely thin layers.
      • US, Canada, Chile, Peru, and China have sizable deposits.

      Disadvantages:

      • Expensive
      • Relatively rare
      • Natural deposits contain traces of radioactive rhenium-187
      • Oh my, traces of a radiocative element! That's a definite no-no! That's worse than traces of peanut!
      • "Higher melting point than silicon"

        That is a bad thing, not a good one.

        "US, Canada, Chile, Peru, and China have sizable deposits."

        Compared to Si, availability is also bad.

        "Expensive"

        By tthe price those things sell (Both Si and MoS2), that is irrelevant.

        "Natural deposits contain traces of radioactive rhenium-187"

        So, those physicists better start working on ruthenium based reactors, we can get a lot of them as a side product.

  • Molybdenum is a CRITICAL trace element in the development of any food crop we have.

    This reeks of the dumbest thing one could do, EVER.

    • by Shihar (153932) on Monday January 31, 2011 @12:22AM (#35053366)

      I'll keep that in mind before I strip mine any farms for molybdenum. Otherwise, I am pretty sure the plants inside of the middle of a mountain are not going to mind.

    • Why exactly is making MoS2 devices the dumbest thing one could do, EVER?
    • by Mr Z (6791) on Monday January 31, 2011 @12:38AM (#35053464) Homepage Journal

      Huh? Just like all the steel we produce somehow reduces the amount of iron plants and animals can make use of? Are you suggesting that a significant fraction of mined molybdenite goes to fertilizer manufacture?

      Molybdenum may not be as abundant as silicon, but it's still fairly abundant. (54th most abundant in the crust and 25th most abundant in sea water, says Wikipedia.) And given its fairly high cost, I imagine any increased demand will be offset by its cost. This would limit molybdenum to niche applications where controlling leakage is a must. I imagine MoS2 based semiconductors would only be cost effective if they can figure out how to use as little of it as possible, perhaps with MoS2 over some other substrate.

      I can think of much stupider things that we could do (and in fact are doing already), such as bottling water, or hyperfocusing food production on corn and subsidizing large quantities of corn-based ethanol production.

      • by Mr Z (6791)
        And actually, it appears that MoS2 over a silicon substrate is exactly what they're proposing. [eurekalert.org] I knew I should have looked at the blowup first.
      • I might add, if you read the article, you would see that it is indeed Molybdenum disulfide on a silicon substrate.

        • by Mr Z (6791)
          Yeah, I missed that. I didn't see it in the article body, but it was obvious when I finally clicked on the image at the right so all the labels were readable.
      • by Kjella (173770)

        I imagine MoS2 based semiconductors would only be cost effective if they can figure out how to use as little of it as possible, perhaps with MoS2 over some other substrate.

        Near as I can tell it's dirt cheap. I figure the cost will be the same as current processors, getting it to ultra-pure quality and the etching process. You can get a kilo of not-so-very-pure MoS2 for about a buck [dhgate.com]. Even silicon good enough to make solar cells costs $67 dollars a kilo [greentechmedia.com] according to this 2009 article. The rest is for turning it from a lump of metal to a working processor.

        • by Mr Z (6791)

          Well, according to Wikipedia, pure molybdenum was going for $30,000 a tonne in August 2009 [wikimedia.org] and before that had shot up to $100,000 a tonne for several years. (That works out to $30 / kilo and $100 / kilo respectively.) I based my cost statement on the higher number on the basis that MoS2 semiconductors would increase the demand.

          I guess that cost puts it on a par with silicon for bulk material cost. More expensive potentially, but not orders of magnitude more like I was thinking. The rest comes, as you s

          • by Kjella (173770)

            I based my cost statement on the higher number on the basis that MoS2 semiconductors would increase the demand.

            Maybe, but that also depends on economics of scale. If it's more of a specialty product today it might go down with volume, unless you run into resource limitations.

            • by Mr Z (6791)

              The spot price of molybdenum was over twice its current price for around 5 years (from ~2004 - 2009). [infomine.com] Given that the drop coincided with the recent economic meltdown, it doesn't seem like a huge leap to suggest that that drop is a direct result of reduced demand

              The steep swing suggests that the annual production of molybdenum is fairly fixed (rather inelastic), at least for the time being. This suggests to me that you would probably have to find new mines or new extraction techniques (say from seawater?)

            • by Mr Z (6791)

              Ok, so I googled around and found this interesting report. [roskill.com] It seems that molybdenum production has more or less kept pace with demand. It appears that the price remained high because demand was leading supply slightly. When demand fell behind supply, the price tanked.

              The report has more detailed insights. Enjoy!

          • by HiThere (15173)

            Recalling history, before silicon was used in transistors, what they called pure silicon had sufficient contaminants that transistors usually couldn't be made from it. They had to improve the purity by about a factor of 10 before it was good enough for single transistor chips.

            I wonder just how pure molybdenum needs to be to be considered pure? I'd guess, just based on history, that the purity will need to be a *lot* higher to use in in integrated circuits. So the price estimate is probably extremely low.

            • by Mr Z (6791)

              Yeah, it wasn't clear to me either how they'd get the MoS2 into the transistor channels either. To build such a thin structure suggests some sort of vapor deposition process if they were to commercialize it.

              Digging through a couple of the links, I finally found what this experiment did in the supplemental information PDF. [nature.com] Their current method doesn't sound like it scales to building arbitrary chips yet:

              Our device fabrication begins with scotch-tape based micromechanical cleavage of commercially available,

      • by PPH (736903)
        Do you really think that making microprocessors with a thin film of MoS2 is going to increase the global demand for the substance beyond that already used for lubricants?
        • by nusuth (520833)

          Lubricant use is pretty niche too; 80% of molybdenum is used in making steel and iron alloys. Granted, that figure includes non-MoS2 use, but electronics industry will probably start synthesis from pure Mo instead of purifying products of existing MoS2 plants.

      • by Chris Burke (6130)

        This would limit molybdenum to niche applications where controlling leakage is a must.

        Which is any application where low power is highly desirable, which includes all applications where you are running off of a battery, which is all of the fastest growing markets for microprocessors.

        That said, I agree it's hard to see how this is going to be a big problem, certainly compared to the much bigger environmental problems we are facing.

        • by Mr Z (6791)
          I was thinking hearing aids and pacemakers might see this long before smartphones, for example.
          • by Chris Burke (6130)

            I think you're probably right, but if it succeeds there, then I would expect demand to rise quite quickly.

    • I'll tell the mining companies to keep that in mind before they turn every atom of Molybdenum in earth's crust over to the semiconductor fabs. Also, I'll ask them not to grind up old chips and dust crops with them. We good?
    • by WillKemp (1338605)

      Don't worry, we're probably going to run out of phosphorous before we run out of molybdenum - and plants are quite partial to that, too.

    • Many other elements are critical trace elements, but I dont see people complaining about using nickel for things like steelmaking.... Simple stating this is dumb without telling people why doesnt help. It's been shown that Mo is used in lubricatanrs for a century or so without problems. Simply saying that a few extra kT is suddently going to cause a problem without saying why doesnt cut ice. After all, we use a lot of moly - no issues so far. We use a lot of copper as well - another trace but that's not a
  • Fuck Yea.

    Lets totally get this ball rolling, and replace as many current devices and server farms as possible. So many people advocate cleaner energy solutions, but neglect the possibility of ridiculously increased efficiency. I say, if we can make retarded huge increases in efficiency, we can significantly reduce our power consumption. Plus, can you image a goddamn smart phone with a week long battery life?? Or a laptop that runs for days without needing to recharge? A server farm that could be powered by

    • You want to save energy by replacing as many of the the currently installed systems in the world? Why do I get the feeling that trashing perfectly good equipment, and manufacturing replacements is not the best use of our energy resources.

      • Replacing a gigawatt server farm with one that uses watts is such a substantial energy savings, that it is difficult to imagine. It would be like replacing a factory with the power usage of a lightbulb and producing just as much. This is a difference of 100,000 times less energy. That is worth it.

        • I think you are probably overestimating the savings from this change. Is the vast amount of energy used in a data center really from leakage in idle transistors? I'm a bit skeptical of that.

          • Most transistors are idle most of the time, and any electron gap below 1.6 eV is going to leak like a an old ladies bladder. Silicon has a gap of 1.1, allowing electrons to cross it with relative ease. Molybdenum disulfide has a gap of 1.8 eV, higher than the charge of a single electron, making it orders of magnitude more difficult to leak any power.

            Think about some basic gates, like the nand, nor, not, and, xor, and, or, the different kinds of flip flops, and think about what percentage of the transistors

      • by Patch86 (1465427)

        Lifespan of most computers being, what, 5 years? 10?

        Wouldn't take long for a decent swathe of the word's install base to move to a new technology, assuming it's worth it.

        • Well yeah, but the OP was saying to take your brand new devices and replace them immediately with this new technology. My point is what you seem to be talking about as well, that it would probably be a better use of resources to replace them when they reach EOL and not sooner.

    • by x0ra (1249540)
      in reality, you will just get more features out of the same die consuming the same amount of power than today. We did great with small CPU, the software we run on them just became full of bloat (not to speak about all the HD crap). That said, Intel's business is to sell you a new CPU every few years, not make it last 15 years.
      • Re: (Score:2, Informative)

        by Belial6 (794905)
        That was true up to a point. Over the last 5 or so years, we hit the 'good enough' point on computers. Power efficiency is where it is at now. With the last round of upgrades in my home, I went from an average power usage of 180kw on my computers to an average of 40kw. That doesn't even include the fact that most of my computers can actually go into stand by now.
        • by Kjella (173770)

          Unless we create a magic battery, power consumption will always be a huge thing for laptops and cell phones. Data centers too certainly measure performance/watt. But I agree, for the regular desktop it's no longer a big deal, if it ever was.

        • by msauve (701917)
          40 kW average? Home? That would be 83 amp service @480V, for a single computer. How many of these supercomputers do you have?
          • by Belial6 (794905)
            Yes, yes... I did mean what. I was going to put the monthly kwh usage but decided I didn't want to go through the math considering the times of use changes better computers brought and so forth. I didn't switch back to watts. Lets just chalk it up to Verizon Math, and move forward. ;)
    • Re:Let me just say (Score:4, Informative)

      by Gaygirlie (1657131) <(gaygirlie) (at) (hotmail.com)> on Monday January 31, 2011 @01:03AM (#35053612) Homepage

      Plus, can you image a goddamn smart phone with a week long battery life?? Or a laptop that runs for days without needing to recharge? A server farm that could be powered by solar power and a few large battery power storage units?

      You have misunderstood the article. It clearly says molybdenite transistors consume 100.000 times less energy than silicon ones in STANDBY. Not when operational. Sure, it would increase efficiency of mobile devices where you turn unneeded transistors off to save energy, but it would do nothing for when the system is operational and in use. Thus your idea of a server farm being solar powered is completely without basis.

      Molybdenite's strength is in mobile applications: when the device is in standby mode it consumes a lot less energy than traditional silicon-based ones. But it has another strength here: silicon is a 3-layer material, whereas molybdenite is monolayer. This means that you can make smaller chips, or cram more stuff in a chip of the same size.

      • Re:Let me just say (Score:4, Insightful)

        by MadnessASAP (1052274) <madnessasap@gmail.com> on Monday January 31, 2011 @02:03AM (#35053854)

        You're doing some freaky ass computing if all the transistors in your CPU are active at the same time.

      • silicon is a 3-layer material, whereas molybdenite is monolayer

        Huh? A MOS transistor is three-layer [eurekalert.org]: Metal, Oxide, Semiconductor, no matter what is the semiconductor.

    • by Andy Dodd (701)

      Well, many people have already addressed the flaws with your argument (such as the energy costs of manufacturing replacements for all this equipment), but more critically, you've failed to realize that this is at such an early stage of discovery that it's still highly likely to fizzle without going anywhere.

      Just because you can make a few samples that perform well in a lab doesn't mean you can produce products with it in a consistent and energy-efficient manner. Just look at gallium arsenide - Two decades

      • Clearly you didn't read the article, and your condescending tone is not just obnoxious, it is pathetic. Come off it.

        The importance of this discovery is held a lot higher than other discoveries precisely because it lacks the various problems of certain materials. First of all, it is just another layer added to silicon chips, the silicon is going to do much work that it already does. Second, it has a high voltage gap that makes it much more efficient and avoids the issues that graphene has in this area, but

  • Oh dear. This means they might have to rename Silicon Valley to Molybdenite Valley, but that doesn't sound nearly as nice.
    • Oh dear. This means they might have to rename Silicon Valley to Molybdenite Valley, but that doesn't sound nearly as nice.

      Valley of the Molls?

    • Molly's Revenge [mollysrevenge.com] are one of the local Irish bands seen here in the Bay Area. (Apparently they were a follow-on to an earlier band called Dance Around Molly, but with a name like "Molly's Revenge" they eventually had to wrote a song involving someone named Molly and some revenge...)

  • by Goldsmith (561202) on Monday January 31, 2011 @12:43AM (#35053494)

    There are plenty of materials out there that make good semiconductors, the question is: can we make them?

    Moly disulfide is a material a couple of different graphene groups have been looking at (hey, we know there's an issue with graphene). What this paper really means is that the Ecole group has figured out how to *make* MoS2 better than other people, and that's really the hard part. Of course, they're still making devices using scotch tape exfoliation...

    It's really hard to mass produce 2D materials.

  • Abundant ... hello? (Score:5, Informative)

    by angel'o'sphere (80593) on Monday January 31, 2011 @12:53AM (#35053550) Homepage Journal
    This mineral, which is abundant in nature, is often used as an element in steel alloys or as an additive in lubricants. That is a joke, isn't it? Or is it just /.? From Wikipedia: Molybdenum is the 54th most abundant element in the Earth's crust and the 25th most abundant element in the oceans, with an average of 10 parts per billion; it is the 42nd most abundant element in the Universe. That is not abundant that is pretty rare. Considering 35% of the planet is silicon ... or is it more? Regards, Angel
    • by KiloByte (825081)

      It is very abundant compared to what is needed for this task, as opposed to some other proposed replacements. It's not like you need tons of molybdenite.

    • by m85476585 (884822) on Monday January 31, 2011 @01:22AM (#35053704)
      How much of that silicon is ultra pure semiconductor grade? Probably none, so both materials need to go through a refining process. If there are areas with high moly concentrations, it doesn't matter how much the rest of the world has, as long as those mines are enough to meet demand (and can continue to do so for a while).
    • by mcelrath (8027) on Monday January 31, 2011 @04:15AM (#35054320) Homepage
      You don't need 10kg of the stuff to make a semiconductor device. Compare it to gold: we produce about 30x more Mo, and you certainly have a few grams of gold somewhere in your house. Anyway my guess is that it might be laid down in layers on top of an insulating substrate (and the substrate doesn't have to be MoS2). So the quantities required are not out of line with production, despite the fact that it is relatively rare in the universe.
    • by Peeteriz (821290)

      From the same wikipedia page - a kilogram of molybdenum costs about 30$, so it's just as abundant as dirt for any practical chip production purposes.

      42nd most abundant element in the universe means that it's about average, as about half elements are rarer. You could call it rare if it was a couple orders of magnitude less abundant, such as gold, palladium or others.

      • Guess what's a popular use of that rare element gold? Electronics is a common use for gold. So if we can afford to use gold, you're saying molybdenite should be not only not a problem, but really makes no sense not to use it for this kind of energy savings.

  • "...Molybdenite's 1.8 electron-volt gap is ideal for transistors and gives it an advantage over graphene (which does not have a gap)..."

    With Graphene, I can scribble it on Scotch Tape [physorg.com] and get a Nobel Prize [wikipedia.org]; can I do that with Molybdenite?
  • ...for recommending the movie "The Brothers O'Toole", look it up.

  • by Anonymous Coward

    Google just announced their new browser update, "Chrome Moly".

  • by cats-paw (34890) on Monday January 31, 2011 @02:38AM (#35054002) Homepage

    let me know when you have I-V curves for a moly disulpide FET. Both p and n types please.

    I learned many moons ago, that one of the most important things about Si is the fact that it's so easy to grow an oxide. It's EXTREMELY useful when processing integrated circuits. Otherwise everything electronic would use III-V's.

    Any new material which aims to replace Si is going to need an equivalent process capability.

    Personally I'm hoping for a breakthrough in organic semiconductors. I want to be able to screen print transistors at home.

    • Re: (Score:3, Insightful)

      by Ranzear (1082021)
      I don't see moly transistors replacing the entirety of silicon transistor applications in the same way that graphene will never replace silicon.

      I can, however, see moly transistors stepping in for the power regulation side of a chip and system where efficiency is demanded, and graphene-based 'burst processing' cores that are shut down completely when not in use on the performance side.

      Everything is about application, adaptation, and integration of technologies, not seeking out a replacement for every e
  • Until humans find a use for it.

It is much easier to suggest solutions when you know nothing about the problem.

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