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Like a forest of fuzzy cotton swabs, microscopic carbon trees of different heights spring from a graphite surface.Ajayan

With a simple heating and cooling process, scientists can grow a forest of microscopic carbon trees on a surface, according to a new study.

In the past, scientists have used catalysts to stimulate the growth of nanotubes and other carbon structures on surfaces (SN: 8/21/99, p. 127). Catalysts, however, can be troublesome, says Pulickel M. Ajayan of Rensselaer Polytechnic Institute in Troy, N.Y. Researchers first have to find appropriate ones and then remove them when the reaction is complete, he explains.

Ajayan and his colleagues instead use a technique called flash chemical vapor deposition. The researchers  bathe a pair of graphite electrodes in methane and helium, heat them quickly and briefly with an electric current, then allow them to cool.

During each heat flash, carbon atoms from the methane settle on the electrodes' surface. Over many heating and cooling cycles, thin cones of carbon with round heads sprout from the graphite. Ajayan and his coworkers report their findings in the March 16 Nature.

"These are really spectacular structures," says Ajayan. "Ultimately, we'd like to grow nanotubes with this technique."

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