A team of researchers at Rensselaer Polytechnic Institute has created hybrid structures that combine the best properties of carbon nanotubes and metal nanowires. The new structures, which are described in a recent issue of
Applied Physics Letters, could help overcome some of the key hurdles to using carbon nanotubes in computer chips, displays, sensors, and many other electronic devices.
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 properties.
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 materials.”
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.
The research was performed under the guidance of Pulickel Ajayan, the Henry Burlage Professor of Materials Science and Engineering at Rensselaer and a world-renowned expert in fabricating nanotube-based materials. Other Rensselaer researchers involved with the project were Robert Vajtai, Derek Benicewicz, Lijie Ci, and M.M. Shaijumon.
Source: Rensselaer Polytechnic Institute
Related stories:
Nanoparticles assemble by millions to encase oil drops
In a development that could lead to new technologies for cleaning up oil spills and polluted groundwater, scientists at Rice University have shown how tiny, stick-shaped particles of metal and carbon can trap oil droplets in water by spontaneously assembling into bag-like sacs.
Nanowires may boost solar cell efficiency, engineers say
University of California, San Diego electrical engineers have created experimental solar cells spiked with nanowires that could lead to highly efficient thin-film solar cells of the future.
Sandia researcher examines the physics of carbon nanotubes
Carbon nanotubes, described as the reigning celebrity of the advanced materials world, are all the rage. Recently researchers at Rice University and Rensselaer Polytechnic Institute used them to make the “blackest black” — the darkest known material, reflecting only 0.045 percent of all light shined on it.
Go Speed Racer! Revving up the world's fastest nanomotors
In a “major step” toward a practical energy source for powering tomorrow’s nanomachines, researchers in Arizona report development of a new generation of sub-microscopic nanomotors that are up to 10 times more powerful than existing motors. Their study is scheduled for the May 27 issue of
ACS Nano journal.
'Sticky nanotubes' hold key to future technologies
Researchers at Purdue University are the first to precisely measure the forces required to peel tiny nanotubes off of other materials, opening up the possibility of creating standards for nano-manufacturing and harnessing a gecko's ability to walk up walls.
Carbon nanotubes outperform copper nanowires as interconnects
Researchers at Rensselaer Polytechnic Institute have created a road map that brings academia and the semiconductor industry one step closer to realizing carbon nanotube interconnects, and alleviating the current bottleneck of information flow that is limiting the potential of computer chips in everything from personal computers to portable music players.
Scientists Make 'Perfect' Nanowires
Scientists have created silicon nanowires that are perfect—at least atomically. Down at the single-atom level, the identical wires have no bumps, bends, or other imperfections. They are perfectly crystalline, even more so than bulk silicon. The full array of nanowires is also highly parallel, and each wire is an excellent metallic conductor.
‘High Q’ Nanowires May be Practical Oscillators
Nanowires grown at the National Institute of Standards and Technology (NIST) have a mechanical “quality factor” at least 10 times higher than reported values for other nanoscale devices such as carbon nanotubes, and comparable to that of commercial quartz crystals. Because a high Q factor indicates a capacity for stable vibrations, the nanowires might be used as oscillators in nano-electromechanical systems for future nano-sensors and communications devices.
