Graphene Sheets Manufactured

The news on graphene keeps getting better as researchers are rushing into print. Now we have the first centimeter sized sheets of graphene and larger sheets are now in sight. If this method can consistently lay down a single layer and I suspect that some irregularity there is not out of place there, then actual recovery may consist of a third laminate layer on top of the graphene itself and a simple chemical elimination of the copper.

That sounds like a manufacturing method to me.

Everyone is looking at the obvious and high end electronics industry and that is exciting, except that we do pretty good there right now. I am much more excited about the the potential for macroscopic applications, were we start playing with sandwiches of graphene, metglas and substances capable of other strange behavior. This is an engineer’s fantasy come true and not just for manufacturing a magnetic exclusion bubble.

I do not know how much good work is stuffed in the literature but we are approaching a time to excavate all that knowledge and find a way to make it all more accessible.

I also now expect to see a flood of new results in physics now that we are learning to manipulate atoms and can imagine sheets of atoms interacting with each other.

May 11, 2009

Large graphene samples could boost carbon electronics

Researchers in Texas are the first to produce centimetre-sized samples of graphene — sheets of carbon one atom thick and dubbed the “wonder material” on account of its unique physical properties. This is significantly larger than existing samples that are typically at the micrometer scale. Richard Piner and his team at the Univeristy of Texas have employed a chemical deposition technique to grow their graphene on thin films of copper.

Graphene holds the promise of revolutionizing electronics over the coming years. One of the main reasons is that electrons travel through graphene with significantly higher mobility than they do in conventional circuits made from silicon. Engineers have already created some rudimentary graphene components, such as
transistors and frequency multipliers. However, making carbon-based circuits will require large and high-quality samples of graphene that can be integrated with silicon.

Wondrous production

Since its discovery in 2004, there have been a range of approaches to isolating graphene from larger samples of carbon. One of the favoured techniques is mechanical exfoliation in which flakes of graphene are stripped from graphite with “sticky tape”. However, due to the delicacy of a material that is just one atom thick, exfoliation typically produces flakes at the nano-scale.

“They say a 30 cm graphene sample is the Holy Grail for carbon electronics but reaching the same order of magnitude is a significant step,” said Richard Piner, one of the researchers at the University of Texas.
Piner and his colleagues take a different approach by growing graphene on a substrate using chemical deposition. Taking a piece of copper foil 25 ┬Ám thick, they add a mixture of methane (CH4) and hydrogen, then heat the apparatus to 1000 degrees Celsius. Single layer graphene is then deposited on the copper in patches up to 1 cm by 1 cm.

Drop the copper

“This very important result may represent the missing link in the industrial fabrication of large area graphene for applications in graphene-based integrated electronics,” said
Roman Sordan, a materials researcher at the Politecnico di Milano.

Previously, researchers had used chemical vaporization but with different metals and this have hindered the quality and scale of carbon growth. For example, nickel has been touted as promising, but carbon is highly soluble in this metal and multiple layers of graphene tend to build up at the grain boundaries.

Now that the team from Texas have produced a large sample of graphene, the next step is to develop a technique for carefully transferring the carbon sheet from the copper to a semiconductor — like silicon. Piner told physicworld.com that initial attempts have resulted in limited success. “We are working on the fact that graphene is extremely hydrophobic and can float to the surface of a liquid… but it is also extremely delicate,” he said.

This research was published in
Science

About the author

James Dacey is a reporter for physicsworld.com

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