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Tuesday, 10 July 2012

Graphene Repairs Holes By Knitting Itself Back Together, Say Physicists

July 10, 2012

The graphene revolution is upon us. If the visionaries are to be believed, the next generation of more or less everything is going to be based on this wonder material--sensors, actuators, transistors and information processors and so on. There seems little that graphene can't do.

But there's one fly in the ointment. Nobody has yet worked out how to make graphene in large, reliable quantities or how to carve and grow it into the shapes necessary for the next generation of devices.

That's largely because it's tricky growing anything into a layer only a single atom thick. But for carbon, it's all the more difficult because of this element's affinity to other atoms, including itself. A carbon sheet will happily curl up and form a tube or a ball or some more exotic shape. It will also react with other atoms nearby, which prevents growth and can even tear graphene apart.

So a better understanding of the way a graphene sheet interacts with itself and its environment is crucial if physicists are ever going to tame this stuff.

Enter Konstantin Novoselov at the University of Manchester and a few pals who have spent more than a few hours staring at graphene sheets through an electron microscope to see how it behaves.

Today, these guys say they've discovered why graphene appears so unpredictable. It turns out that if you make a hole in graphene, the material automatically knits itself back together again.

Novoselov and co made their discovery by etching tiny holes into a graphene sheet using an electron beam and watching what happens next using an electron microscope. They also added a few atoms of palladium or nickel, which catalyse the dissociation of carbon bonds and bind to the edges of the holes making them stable.

They found that the size of the holes depended on the number of metal atoms they added--more metal atoms can stabilise bigger holes.

But here's the curious thing. If they also added extra carbon atoms to the mix, these displaced the the metal atoms and reknitted the holes back together again.

Novoselov and co say the structure of the repaired area depends on the form in which the carbon is available. So when available as a hydrocarbon, the repairs tend to contain non-hexagonal defects where foreign atoms have entered the structure.

But when the carbon is available in pure form, the repairs are perfect and form pristine graphene.

That's important because it immediately suggests a way to grow graphene into almost any shape using the careful injection of metal and carbon atoms.

But there are significant challenges ahead. One important question is how quickly these processes occur and whether they can be controlled with the precision and reliability necessary for device manufacture.

Novoselov is a world leader in this area and the joint recipient of the Nobel Prize for physics in 2010 for his early work on graphene. He and his team are well set up to solve this and various related questions.

But with the future of computing (and almost everything else) at stake, there's bound to be plenty of competitors snapping at their heels.

Source: Technology Review

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