Many research teams are working to make
electronics that include carbon nanotubes -- rolled-up sheets of carbon
atoms that have useful electrical properties and that can be as narrow
as the span of four hydrogen atoms.
Researchers from the University of California at Berkeley and
Stanford University have fabricated a circuit that combines carbon nanotube
transistors and traditional silicon transistors on one computer chip.
Connecting minuscule nanotube transistors to traditional silicon transistors
enables the atomic-scale electronics to communicate with existing electronic
Such integrated nanotube-silicon circuits could enable super-sensitive
sensors that distinguish among thousands of chemical or biological agents
and ultra-high-density memory chips that store 100 times the information
of today's state-of-the-art memory chips, according to the researchers.
The researchers grew carbon nanotubes on portions of a silicon
chip that contained connections made from molybdenum, a metal able to
withstand the high temperatures needed to grow the nanotubes. The prototype
chip contains thousands of silicon transistors and hundreds of nanotube
The silicon transistors were configured in an 11-level binary
tree that allowed for individual access to all the nanotube transistors
using only 22 input signals.
The researchers' chip is designed to rapidly evaluate the electrical
properties of large numbers of nanotubes, which will help researchers
optimize nanotube growth processes. It can be used for that purpose now.
More broadly practical carbon nanotube-silicon transistor chips could
be built in five to ten years, according to the researchers.
The work appeared in the January, 2004 issue of Nano Letters.
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