Monday, May 09, 2005

"NANOTECH: Nanowires look promising for plastic circuits"

Silicon nanowires could combine the best features of carbon nanotubes and amorphous silicon to overcome the liabilities of the circuit technologies being explored for large-area flexible substrates, research at Harvard University suggests. Potential applications for such substrates include disposable e-newspapers and wall-hanging displays. Two of the candidates, amorphous silicon and organic semiconductors, are inherently slower than silicon. And while carbon nanotube transistors promise higher electron mobility than is possible with silicon, the tubes have not yet been demonstrated in an integrated circuit. The payoff of the Harvard work, the researchers maintain, will be a material with the electron mobility of nanotubes but with the low-temperature processing of organic semiconductors. The team demonstrated a nanowire-based ring oscillator that operated at 12 MHz. While that is dismally slow by CMOS standards, it's still 20 times faster than today's integrated organic semiconductors. The researchers believe they can scale the approach to CMOS speeds in the future. "We are not exploiting nano to build ultrasmall nanoscale devices; we are exploiting it to bring high-performance devices to an application area where the only competing materials are . . . low-performance or low-mobility materials," said Harvard professor Charles Lieber, who designed the ring oscillator chip with Harvard EE Donhee Ham.