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?

[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: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.