NEW ROUTE TO GRAPHENE DEVICES - C&EN Global Enterprise

Apr 11, 2011 - The goal is to use graphene to make circuit elements that are smaller and that outperform today's devices. With that goal in mind, a nu...
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NEWS OF THE WEEK

CONGRESS SPLITS ON EPA CO2 BILL

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CLIMATE CHANGE: Senate blocks, House backs legislation to ban EPA controls on greenhouse gases

McConnell says EPA’s CO2 regulations will hurt jobs.

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ENATORS HOPING to stop EPA from regulating

carbon dioxide and other greenhouse gases failed to muster sufficient votes to do so last week. But the House of Representatives did exactly the opposite and passed a bill (H.R. 910) on a 255–172 vote to bar EPA from cutting CO2 emissions under the Clean Air Act. The Senate action centered on four amendments to an unrelated bill to help small businesses. Garnering the most support was an amendment by Minority Leader Mitch McConnell (R-Ky.). McConnell’s proposal and H.R. 910 would alter the Clean Air Act to prevent EPA from using that law to regulate emissions of CO2 and other greenhouse gases. Both measures also would nullify the agency’s scientific finding that greenhouse gas accumulation in the atmosphere endangers public health (C&EN, March 14, page 9). McConnell’s proposal attracted 50 votes, including

NEW ROUTE TO GRAPHENE DEVICES NANOELECTRONICS: Procedure

PHAE DON AVOURI S/IB M

Fabricating transistors with a nanometer-long strip of graphene on diamond-like carbon nudges these nanoscale devices toward commercialization.

draws on industry-compatible methods and materials

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NEW STRATEGY for fabricating graphene-

based transistors—one that relies on materials and methods compatible with those used in the microelectronics industry—has been developed by researchers at IBM (Nature, DOI: 10.1038/nature09979). The work may lead to commercially viable techniques for manufacturing electronic devices that exploit the unique properties of graphene, a layer of carbon one atom thick. Graphene’s outstanding electronic and other properties have sparked a wave of research aimed at making circuit components based on the ultrathin material. The goal is to use graphene to make circuit elements WWW.CEN-ONLINE.ORG

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four from Democrats, but failed because it needed 60 supporters to prevent a filibuster. By large margins, the Senate rejected other amendments to limit or delay EPA’s regulations, offered by Sens. Max Baucus (D-Mont.), John D. Rockefeller (D-W.Va.), and Debbie A. Stabenow (D-Mich.). Fred Krupp, president of Environmental Defense Fund, an activist group, characterizes the legislative efforts as “an unprecedented assault on public health protections under the Clean Air Act.” In contrast, Calvin M. Dooley, president and CEO of the American Chemistry Council, urges Congress to block EPA so “business growth and hiring can continue.” The agency’s plan to regulate CO2 is in development. Under a schedule reached through a settlement in federal court, only the largest emitters will be covered in the next few years. By mid- to late 2012, refineries and electric utilities will begin implementing regulations that EPA will develop this year through discussions with industry. Those rules are most likely to call for greater energy efficiency (C&EN, Jan. 10, page 7). A statement from the White House applauded the Senate action and backed what it called “EPA’s common-sense steps to safeguard Americans from harmful pollution.” If the Senate passes a bill similar to H.R. 910, President Barack Obama is likely to veto it, the White House says.—CHERYL HOGUE AND JEFF JOHNSON

that are smaller and that outperform today’s devices. With that goal in mind, a number of research teams have incorporated graphene electrodes into radiofrequency (RF) transistors, fast-acting signal amplifiers that play a central role in wireless communication systems. But the graphene electrodes in the fastest of those transistors are prepared by a laborious manual procedure. Graphene can be prepared more efficiently in larger batches via vapor deposition methods. But those procedures generally call for depositing the film on a layer of silicon dioxide, which adversely affects the electronic performance of graphene devices. To sidestep those limitations, Yanqing Wu, Yu-ming Lin, Phaedon Avouris, and coworkers at IBM’s Thomas J. Watson Research Center developed a vapor deposition method in which graphene ends up on diamondlike carbon, a material well-known to the semiconductor industry with desirable electronic properties. Initial tests show that RF transistors made via the new method operate at very high frequencies and work well even at cryogenic temperatures. “The approach of the IBM team is very interesting because it is compatible with common semiconductor processing,” says Frank Schwierz, a device physicist at the Technical University of Ilmenau, in Germany. At this early stage, before the fabrication method has been optimized, Schwierz is cautious about calling the technique a breakthrough. “But it may turn out to be very useful in the future,” he says.—MITCH JACOBY

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