Carbon-metal hybrid nanowires open door to new nanoelectronic devices
9 January 2007
Hybrid structures that combine the best properties of carbon nanotubes
and metal nanowires could lead to new applications in computer chips,
displays, sensors and other electronic devices.
The new structures were created by a team of researchers at Rensselaer
Polytechnic Institute and are described in a recent issue of Applied
|Junction between a
gold nanowire (top) and a carbon nanotube.
The impressive conductivity of carbon nanotubes makes them promising
materials for a wide variety of electronic applications, but techniques to
attach individual nanotubes to metal contacts have proven challenging. The
new approach allows the precise attachment of carbon nanotubes to individual
metal pins, offering a practical solution to the problem of using carbon
nanotubes as interconnects and devices in computer chips.
“This technique allows us to bridge different pieces of the
nanoelectronics puzzle, taking us a step closer to the realization of
nanotube-based electronics,” said Fung Suong Ou, the paper’s corresponding
author and a graduate student in materials science and electrical
engineering at Rensselaer.
As chip designers seek to continually increase computing power, they are
looking to shrink the dimensions of chip components to the nanometer scale,
or about 1-100 billionths of a meter. Carbon nanotubes and nanowires that
became available in the 1990s are promising candidates to act as connections
at this scale, according to Ou, because they both possess interesting
For example, carbon nanotubes display amazing mechanical strength, and
they are excellent conductors of electricity, with the capacity to produce
interconnects that are many times faster than current interconnects based on
copper. Gold nanowires also have very interesting optical and electrical
properties, and they are compatible with biological applications, Ou said.
“In order to take full advantage of these materials, we demonstrate the
idea of combining them to make the next generation of hybrid nanomaterials,”
he said. “This approach is a good method to marry the strengths of the two
The metal nanowires in this technique are made using an alumina template
that can be designed to have pore sizes in the nanometer range. Copper or
gold wires are deposited inside the pores, and then the entire assembly is
placed in a furnace, where a carbon-rich compound is present. When the
furnace is heated to high temperatures, the carbon atoms arrange themselves
along the channel wall of the template and the carbon nanotubes grow
directly on top of the copper wires.
“It’s a really easy technique, and it could be applied to a lot of other
materials,” Ou said. “The most exciting aspect is that it allows you to
manipulate and control the junctions between nanotubes and nanowires over
several hundred microns of length. The alumina templates are already
mass-produced for use in the filter industry, and the technique can be
easily scaled up for industrial use.”
To date the team has made hybrid nanowires that combine carbon nanotubes
with both copper and gold. But they also are currently working to connect
carbon nanotubes to a semiconductor material, which could be used as a
diode, according to Ou.