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The new head of the National Center for Science Education promises to "fight the good fight" against attacks on...
Analyses of the H7N9 strains isolated from four new cases show that the virus is evolving rapidly, heightening anxiety...
In 2009, Jack Szostak shared a Nobel Prize for his part in discovering the role of telomeres, the end bits of...
Science has exposed a thriving academic black market in China involving shady agencies, corrupt scientists, and...
Paper-selling agencies flourish in the aura of reputable businesses. For some scientists, it may be difficult to tell...
Data collected by satellites and floating probes have chronicled a 2-decade rise in the temperature and thickness of a...
Cholesterol, the artery-clogging molecule that contributes to cardiovascular disease, has another nasty trick up its...
Until recently, the Defense Advanced Research Projects Agency (DARPA) kept its plans for its $70 million portion of the...
- 27 November 2013 12:59 pm , Vol. 342 , #6162
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Turning Down the Heat on Nanowires
30 June 2003 (All day)
Nanometer-scale wires are stronger and more capable of conducting heat than the average wire, but manufacturing them or their cousins, nanotubes, is difficult and mass production is currently impossible. In an attempt to break that barrier, researchers have taken a small step toward producing nanowires and nanotubes directly on silicon chips.
One reason it's tricky to make and hook up nanowires, made of single-crystal silicon, or nanotubes, made of molecule-thick sheets of carbon, is that they are fragile and can easily break when transported from one substrate to another. Their synthesis also requires temperatures high enough to destroy silicon microelectronics, such as computer chips on which nanowires or nanotubes might carry out faster computations than less dainty connections. But a research group at the University of California, Berkeley, has worked out a method of localizing the heat in order to assemble nanowires right on a chip at room temperature.
The team, led by mechanical engineer Liwei Lin, placed microelectromechanical systems, or MEMS, in tiny bridges on an etched silicon chip. The MEMS bridges acted as resistors, carrying temperatures of up to 1400°C, while micrometers away the chip itself was at room temperature. The experimenters introduced acetylene or silane into the vacuum chamber as sources of carbon or silicon, respectively. Nanowires grew from the MEMS to lengths of 5 to 10 micrometers all anchored at one end to the MEMS bridges, the team reports in the 30 June issue of Applied Physics Letters. The next step, says Lin, is to find a way to get the wires or tubes to anchor at the other end, which would provide a complete nanowire or nanotube right on the chip.
The research "opens up a new possible way that one could pursue in integrating nanostructures with microstructures," says Charles Lieber, a nanotechnologist at Harvard University. In principle, the team could grow silicon nanowires in one region of a chip and then switch to grow carbon nanotubes in another spot, but so far, "they don't have a lot of control over the growth," he says. "The idea is a nice idea," Lieber says. "How important it is beyond that, it's a little early to say."
Liwei Lin's home page