News IBM: Graphene won't replace silicon in CPUs

Graphene can't fully replace silicon inside CPUs, but it could be used in hybrid chips.

http://www.bit-tech.net/news/hardware/2011/01/21/ibm-graphene-wont-replace-silicon-cpus/1

 

can someone explain "small on/off ratio" to me. does "can't be switched off" mean that once electricity is applied to it the charge is never dissipated?

 

It means a small ratio between the current flowing through the transistor when it is on, and the current flowing when it is off. In a normal transistor that is turned off, only a tiny amount of "leakage" current can flow, meaning that the ratio between on and off is much higher. A chip made from transistors that leak alot of current when they are turned off would waste alot of energy, and therefore produce alot of heat.

 

The bigger issue than heat is signalling. If a computer can't tell the difference between a 0 (gate closed) and a 1 (gate open) then the whole thing breaks down. in silicon gates the difference a 1 and a 0 is a lot, with graphene it is not as much and so the bits are harder to read.

 

Graphene will also run cooler than silicon. A hybrid chip sounds like a very good idea.

 

Hybrid chips sound a good idea for most applications. Although for the high-end computing IBM makes it's money in, having mainly graphene chips would make sense.

Can't help think what Intel could do with this and its turboboost technology. Maybe for the Core i13 maybe?

 

thats exactly right. what picky88 said is true, but what you said is the more significant problem.

however, shouldn't the solution be as simple as just decreasing the wattage of a cpu? i don't see how graphene can even be considered a transistor if it doesn't even turn off. as another question, how would you manage to do a hybrid of graphene and silicon? to me thats like mixing water with vegetable oil - it CAN be done but they just don't mix because of how different they are, even though they are both liquids. silicon and graphene can both be transistors but they operate so differently that i don't understand how a hybrid could be possible.

 

@KM-S the trouble is you can't just do a straight hybrid chip - it's not like a hybrid car where both systems do the same thing. As Cthippo said, with a low ratio the computer won't be able to differentiate between the two signals, thus it cannot (at least right now) be used for a lot of the functions silicon is used for, in particular pretty much everything silicon does in computer IC's.

It sounded like a dream when I first read about this. The cynic in me said there must be a catch and I guess this is it. I have a feeling now, while getting graphene transistors usable for logic circuitry might be cracked eventually, it just won't be all that practical and end up being on the expensive shelf along with gallium-arsenide and other exotic material substrates.

 

I'm sick of hearing about how 'great' graphene is, when in most applications it's just a fad.

 

A transistor doesn't need to be able to output a zero to be a transistor, it just needs to be able to output a variable amount of current, depending on the input.

Anyways, please see this illustration from wikipedia regarding bandgap:



The bandgap represents input voltage range where the semiconductor is able to output a "0". In silicone, that is pretty large at 1.1eV. Graphene's bandgap, even in the best dual-layer designs is from 0-0.25eV.

Currently, the bandgap for graphene is smaller than a single unbound electron (1eV), meaning it's effectively useless for making computer chips because we can't even make it send a zero.

 

It did win a Nobel prize this year, there must be some substance in it.

New technologies regularly start out with a notion that seems crazy and unworkable to most, but with such huge amounts of time and money going into this research the benefits of graphene will eventually be harnessed and made into a practical application.

I'm really looking forward to this article, Custom PC have done some brilliant features recently, I especially liked all the broadband companies being named and shamed in issue 90.

 

Obama won one for world peace... 'nuff said...

 

Not world peace, just peace.

 

This still has a lot of potential. Hopefully they will find a way to turn them off, but even if they don't it's not the end for Graphene. Many things have been thought up with a specific use in mind, only for it to be later discovered that they can actually be used for something else. So even if this can't help much with chips someone will eventually find a good use for it.

Can't wait to read the article in Custom PC!

 

I'm wondering if instead of being able to make them more "off", if it's possible to make whatever they hook into more sensitive to the differences between "on" and "off".

 

One of the primary values of Carbon is that it can be programmability changed from a P junction to N junction it is well known that high temperature super conductivity requires materials that provide an electron gap for example Iridium Oxide - I agree that graphene will not directly replace silicon in current chip designs however no one said we must use carbon by itself. For example Iridium Oxide provides the necessary electron gap to completely switch off the electron flow.

I suspect we will begin to see a new basis for chip design; carbon is only one of the key elements necessary to make it happen.

 

Of course!

The voltage/current is taken as an analogue > converted to digital.

e.g. Digital is either 1 or 0. With the analogue interpretation you could take anything up to 85% as a 0. anything greater than 85% as a 1.

or does that negate the effect of the CPU - having to have some form of secondary (software) detection?

 

the could just find a new way to shut a graphene cpu off... i mean it can't be to hard to invent a different process or have a start-up processor that activated a graphene processor?

 

To everyone saying that 'they should just change the design'; That is not really possible. In my own measurements it shows that graphite (multiple layers of graphene) doesn't have a real non-0 voltage, 0 ampere area.

(my measurement on a student version STM)
while for silicon it does have that area.
http://turboblogsite.com/wp-content/uploads/2010/05/20.jpg
(not my measurements)

This basically means that with silicon you can have an area that outputs (near) 0 ampere over a large voltage range, while for graphene it is way harder to make a near 0 output.

 

I assume you mean carbon can be either n- or p-doped? The same way that Si can? Even if you did dope graphene to be a p- or n- material, you'd seriously affect the properties that make it so special. For example the fact that it's one atom thick....

Also you can't change from a p-junction to an n-junction, you have p and n doped semi-conductors that form a p-n junction .

Please do tell me how you'd use IrO2 to provide the band-gap to essentially form the p-n junction and thus the overall transistor? More to the point the cost of IrO2 can't be relied upon and as it stands, Si works just fine and the manufacturing processes are just dandy for what we need.