Carbon Research May Boost Nanoelectronics

　　Lawrence Livermore National Laboratory scientists have investigated a way to create linear chains of carbon atoms fromlaser-melted graphite. The material, called carbyne, could have a number ofnovel properties, including the ability to adjust the amount of electricalcurrent traveling through a circuit, depending on the user’s needs.

　　Carbyne is the subject of intense research because of its presence inastrophysical bodies, as well as its potential use in nanoelectronic devicesand superhard materials. Its linear shape gives it unique electrical propertiesthat are sensitive to stretching and bending, and it is 40 times stiffer thandiamond. It also was found in the Murchison and Allende meteorites and could bean ingredient of interstellar dust.

　　Using computer simulations, LLNL scientist Nir Goldman and colleagueChristopher Cannella, an undergraduate summer researcher from Caltech,initially intended to study the properties of liquid carbon as it evaporates,after being formed by shining a laser beam on the surface of graphite. Thelaser can heat the graphite surface to a few thousands of degrees, which thenforms a fairly volatile droplet. To their surprise, as the liquid dropletevaporated and cooled in their simulations, it formed bundles of linear chainsof carbon atoms.

　　“There’s been a lot of speculation about how to make carbyne and how stableit is,” Goldman said. “We showed that laser melting of graphite is one viableavenue for its synthesis. If you regulate carbyne synthesis in a controlledway, it could have applications as a new material for a number of differentresearch areas, including as a tunable semiconductor or even for hydrogenstorage.

　　“Our method shows that carbyne can be formed easily in the laboratory orotherwise. The process also could occur in astrophysical bodies or in theinterstellar medium, where carbon-containing material can be exposed torelatively high temperatures and carbon can liquefy.”

　　Goldman’s study and computational models allow for direct comparison withexperiments and can help determine parameters for synthesis of carbon-basedmaterials with potentially exotic properties.

　　“Our simulations indicate a possible mechanism for carbyne fiber synthesisthat confirms previous experimental observation of its formation,” Goldmansaid. “These results help determine one set of thermodynamic conditions for itssynthesis and could account for its detection in meteorites resulting fromhigh-pressure conditions due to impact.”