Replacing Copper With Pencil Graphite

Late-Eight writes "A key discovery at Rensselaer Polytechnic Institute could help advance the role of graphene as a possible heir to copper and silicon in nanoelectronics. Researchers believe graphene's extremely efficient conductive properties can be exploited for use in nanoelectronics. Graphene, a one-atom-thick sheet of carbon, eluded scientists for years but was finally made in the laboratory in 2004 with the help of everyday, store-bought transparent tape. The current research, which shows a way to control the conductivity of graphene, is an important first step towards mass producing metallic graphene that could one day replace copper as the primary interconnect material on nearly all computer chips." Researchers are now hot to pursue graphene for this purpose over the previous favorite candidate, buckytubes (which are just rolled-up graphene). Farther down the road, semiconducting graphene might take over from silicon at the heart of logic chips.

Re:There are even more advantages

[John Sokol]

Sorry, ( I mean thermal conductivities) watt per square meter kelvin[W/(mK)] I use WMK
To put this into perspective Steel is around 60 WMK, Silicon 149 WMK , Aluminum is 200 WKM, Copper is 400 WMK

And some nanotubes where reported as almost 10,000 WMK

Somehow I thought Silicon was more like 60wmk but is higher according to http://en.wikipedia.org/wiki/Silicon [wikipedia.org]

Re:Way back when....

[LiquidCoooled]

The Pencil trick is also useful for reconnecting the bridges on the original Duron/Athlon chips.

Pushing the cpu up from 650 to 800mhz made *all* the difference...

Re:There are even more advantages

[Anonymous Coward]

Nanotubes are different from rolled up graphene. Nanotubes are like straws, generally cylindrical. Rolled up graphene usually refers to a fruit-roll-up type of structure where it isn't a contiguous cylinder.

Re:There are even more advantages

[ookabooka]

And to karma whore a bit Diamond ranges from 900 - 2320 WMK (type iia) being 2,320 WMK. The fact that diamons (excluding some blue diamonds) are also great insulators is worth noting as it makes it interesting for integrating into electronics; it won't interfere with the circuits but will happily carry away heat.

Pencil Trick

[Taleron]

A common method for unlocking old Athlon and Duron processors was using a good old pencil to connect the bridges. They're catching on!

Re:Way back when....

[Mal-2]

There was a time when you could unlock the multiplier on an Athlon chip with a pencil as well. When AMD went from the ceramic to the "organic" packaging, this no longer worked -- you needed a conductive pen instead, which was still possible, but more error-prone. After all, you can just erase a stray pencil mark, and the silver pen ink tends to spread unless you tape off adjacent areas.

I don't know if these pens were readily available (though I bet they existed) when you had to repair your old Atari, but one of them would have provided a permanent solution to your problem.

The problem with using pencils to fix broken traces is that there is a high resistance -- not so much within any one flake of graphite, but in the gaps between them. As the trace gets longer and/or thinner, that resistance goes up until the device just stops working. A single sheet or ribbon of graphene would neatly sidestep the issue this causes.

Mal-2

Re:Huh? Getting Annoying

[Anonymous Coward]

Sir, Graphite is used in pencils, Graphene is just sheet of Graphite.

"Graphenes are the 2-D counterparts of 3-D graphite." http://en.wikipedia.org/wiki/Graphene [wikipedia.org]
"Graphite (named by Abraham Gottlob Werner in 1789 from the Greek (graphein): "to draw/write", for its use in pencils) is one of the allotropes of carbon." http://en.wikipedia.org/wiki/Graphite [wikipedia.org]

Re:pencils conduct electricity

[ross.w]

Also possible to disable someone's car (when they had distributors) by removing the distributor cap and drawing a line from the centre to the outside using a pencil. High voltage tracks the pencil line to ground - car won't start.

They should talk to the chip bakers first....

[Ancient_Hacker]

Ahem, perhaps these pencil-pushers should talk to actual chip makers and bakers first before speculating on the applications of graphene. Anything that's only one atom thick isn't compatible with current or any forseeable IC process. Chips have to undergo many heating, cooling, deposition, and diffusion steps before they're done. Anything one-atom thick is going to diffuse away in the process. You also have the reliability problem-- you need reliable connections, millions of them. Anything one-atom thick is going to have too many defects.

Bah, Physicists! They got it all wrong again.

[Chemisor]

Bah, Physicists and their QM simulations! They got it all wrong again. It isn't the length of the graphene ribbon that affects its properties, but the shape of its edges. If you look at benzene ring's molecular orbitals, you'll see that there are two ways to pack them in a ribbon. If they all line up, with resonant transfer going along the ribbon in a straight line, then you have metallic conductivity, with the electron just gliding across all the orbitals without hitting any gaps. If the orbitals don't line up, you end up with little dead ends here and there, which cause "turbulence" and reduce conductivity.

Now, the packing of the orbitals is determined by the edges because of their constraints on orbital orientation. In the middle of the ribbon, you have a pure hex grid, and the orbitals, which can be visualized as taking half of each hex and painting a large C on it (these are not the same as the three bonding pi orbitals). Try it yourself: draw a hex grid and try to pack Cs. To visualize resonance, push on one end of a C and see how to repack the resulting structure. In the middle, you have three orientations at every node, but at the edges you don't. The more edges you have, the more constraints there are on the packing, and the more likely it is that the oribitals in the middle won't be in resonance with each other in a given direction. When you push on a C in such a grid, it will push other Cs sideways instead of along the ribbon, causing "resistance".

There are two types of edges, familiar to tile game developers as the vertical and horizontal orientation. In the horizontal packing, the flat side of each hex is bordering the edge, in the vertical the flat side is perpendicular to the edge. It turns out that if you have horizontal edges on your graphene ribbon, it is metallic; if you have vertical ones, it is semiconductive (which is another way of saying it has more resistance). If the edges are not quite straight, which will quite likely happen if you are making your ribbons via CVD or duct tape or something, you'll see a mix of both behaviors, resulting in a conductivity somewhere in between full-out and almost-nothing.

This is the trouble with modern physics - they just don't care about reality any more. If they only drew a few pictures, like real chemists do, they'd have seen this very easily. Instead they waste their time on simulations that only give them numbers they don't know how to interpret. Sheesh.

Re:What about housing wires?

[ivan256]

They already do. Long haul high-tension wires are copper on the outside, and either aluminum, steel, or composite fiber on the inside.

Of course, the reasoning isn't what the GP was saying. They actually do it do balance the conductivity with the weight of the wire since the cable needs both high conductivity and the ability to support itself without breaking or sagging too far.

Yes

[marcosdumay]

"wouldn't quantum effects become a problem at that scale?"

Quantum effects create the properties those people are looking for.

Graphene is a great story

[mentaldrano]

There is a lot of interest in graphene these days among physicists - if you're interested, Google "massless Dirac fermion" for more info, or check pretty much any recent issue of Science or Nature.

The electrical engineers however, have said "meh." Graphene is a decent electrical conductor if you dope it with something - not as good as copper, but decent. It does have great thermal conductivity, though. The big problem with graphene is that you can't really make it in big sheets or long wires. The "tape" method is a great hack - simply stick the tape onto a chunk of graphite, then peel it off and stick it on a substrate (glass or silicon), then peel it off again. Odds are, now you have a sheet of graphene stuck to your substrate, somewhere. Bad news: the biggest piece you're likely to find will be 1-10 micrometers long, and you'll need an electron microscope to find it. This is great for investigating the electrical or thermal properties of graphene, but as for manufacturing, forget it.

As for graphene transistors, those are out too. Transistors should have a very high resistance when "off," and graphene doesn't. The maximum resistance a sheet of graphene can have is about 6 kiloOhms for a square sheet. Fundamentally, graphene is a semiconductor like silicon or germanium, but its band gap is zero, which basically means it can never be "off."

'Drano