July 11, 2012

Graphene Found To Be Self-Repairing

redOrbit Staff & Wire Reports - Your Universe Online

Researchers are one step closer to solving the mysteries of graphene, the carbon allotrope that could be the basis for the next generation of sensors, transistors, processors and more - if scientists can find a way to produce it in large quantities and mold it into the shape necessary to power future devices.

One of the major problems with the material is that it is difficult to grow it into a layer that is only a single atom thick. This is especially problematic since graphene is made of carbon, which has a natural affinity to other atoms (including itself), the MIT Technology Review reported in a Tuesday article.

That affinity causes a sheet of carbon to react with other atoms nearby, thus preventing growth and possibly ripping the graphene apart. In order to gain a better understanding of this material and the way it interacts both with itself and the surrounding environment, University of Manchester physicist Konstantin Novoselov and colleagues analyzed graphene sheets using an electron microscope.

They discovered that if you make a hole in the substance, it automatically repairs itself.

"Nano-holes, etched under an electron beam at room temperature in single-layer graphene sheets as a result of their interaction with metal impurities, are shown to heal spontaneously by filling up with either non-hexagon, graphene-like, or perfect hexagon 2D structures," Novoselov, a Nobel Prize winner in 2010 for his work with the material, and his colleagues explained in a paper detailing their work.

"Scanning transmission electron microscopy was employed to capture the healing process and study atom-by-atom the re-grown structure," they added. "A combination of these nano-scale etching and re-knitting processes could lead to new graphene tailoring approaches."

According to the MIT Technology Review, the scientists basically etched small holes into a sheet of graphene using an electron beam, then monitored the reaction using an electron microscope. They also added a few palladium or nickel atoms, which acted as a catalyst for the dissociation of the carbon bonds and bind to the edges of the holes for stability.

Novoselov's team found that the holes grew larger when a greater number of metal atoms were added, since they were able to stabilize larger holes, and that the addition of extra carbon atoms displaced the metal atoms, helping close the holes and knit the material back together.

The structure of the repair depends upon the form of the carbon used, the researchers told MIT, but even when pure carbon is used, the repairs "are perfect and form pristine graphene." That discovery could be used to help developers grow or mold graphene into essentially any shape using a variation of carbon and metal atoms, though more work will be required to determine how quickly the processor occur and whether or not they can be precisely and reliably controlled at a level that will permit the manufacturing of technological devices.