Molybdenite As an Alternative To Silicon

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)."

Comments

Molykote?

[cvtan]

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

Re:Molykote?

[pwagland]

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

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.

Re:Molykote?

[arivanov]

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.

reduction in subthreshold leakage current

[RichMan]

In the latest technologies a lot of current is wasted to subthreshold conduction . 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.

Re:reduction in subthreshold leakage current

[MagusSlurpy]

That would be the band gap.

Re:reduction in subthreshold leakage current

[GospelHead821]

In insulators, there are no energy states that involve conductive electrons. In conductors, all of the energy states involve conductive electrons. In semiconductors, electrons normally reside in a nonconductive state but you can inject some energy and the electrons will be raised to a conductive state. The amount of energy required to raise the electrons to a conductive state is that semiconductor's gap.

Re:Make better computers, kill more plants

[Shihar]

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.

Re:Make better computers, kill more plants

[Mr Z]

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.

finding a good material is not the problem

[Goldsmith]

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?

[angel'o'sphere]

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

Re:Abundant ... hello?

[m85476585]

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).

Re:Abundant ... hello?

[dakameleon]

It's pretty convenient that the US also happens to be the world's largest producer of the stuff too: http://en.wikipedia.org/wiki/File:2005molybdenum_(mined).PNG

Re:Abundant ... hello?

[mcelrath]

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.

Re:Abundant ... hello?

[Namarrgon]

That table you linked to says the annual production of molybdenum is 80 kilotonnes, which is not exactly rare.

It also says that the annual production of electronics-grade silicon is only 5 kilotonnes, so our needs aren't going to be a problem.

Re:Let me just say

[Gaygirlie]

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:Make better computers, kill more plants

[Shihar]

Um, okay. You can pass on my TED talks. Otherwise, the point stands.

Molybdenum is generally gathered as a byproduct of other mining operations. The "free" molybdenum in soil that plants uses is utterly unaffected when you tear open a mountain to get at it. The original point of "OMG BUT PLANTS USE IT!" was dumb and reactionary. Hell, just re-read the original post if you are in doubt. This is like if someone declared that they found a novel use for nitrogen and someone else freaked out be cause OMFG nitrogen is critical for all life!!!11!!

There are actual legitimate road blocks to using molybdenum in place of silicon. OMFG the plants!11!!! isn't one of them.

Re:Let me just say

[MadnessASAP]

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

great, more advertising by press release

[cats-paw]

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:great, more advertising by press release

[Ranzear]

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 end of the spectrum at once. Silicon is the Jack in the middle, while the specialists should be looked upon as integrable to the whole of transistor arrangement.