Published on August 27th, 2013 | by Tina Casey3
Cheap Substitute For Silicon Grows From Carbon Nanotube “Seeds”
While we’ve been busy touting graphene as the “miracle material of the new millennium,” there’s another advanced materials kid on the block called carbon nanotubes and they haven’t exactly been on the snooze either. A team of researchers at the University of Southern California (USC) has just announced that they’ve cracked the code for cooking up single-walled carbon nanotubes with precise atomic structures. If the process can be scaled up, carbon nanotubes could substitute for silicon to usher in a new era of smaller, faster, more energy efficient computers and other electronic devices.
Growing Carbon Nanotubes From Seeds
For those of you new to the topic, carbon nanotubes are cylinders of carbon atoms no more than one nanometer (one billionth of a meter) thick. As low cost, highly efficient semiconductors they have endless potential applications.
The obstacle has been to identify fabrication methods that enable the mass production of carbon nanotubes with a precise structure. Left to grow with the help of a catalyst, carbon nanotubes form random twists called chiralities, along with an annoying byproduct called plain old soot.
The new finding builds on a collaboration with the National Institute of Standards and Technology (NIST), which prefers a “cloning” analogy, but for now let’s go with USC’s preference for agricultural references and call this a method for growing carbon nanotubes from precisely engineered “seeds.”
Between the USC and NIST teams, the early research had progressed to the point of using DNA molecules as a kind of binder that forces carbon nanotubes to grow with one specific chirality, eliminating the need for a catalyst. That line of investigation stalled temporarily when it was found that the technique worked only on short pieces of nanotube.
Last year, the research regained momentum with the development of a workaround solution for growing longer strands without a catalyst:
Small segments of nanotubes of identical chirality, extracted using the DNA technique, were put in a high-temperature reaction chamber at USC with methane gas, which breaks down in the heat to smaller carbon molecules that attach themselves to the ends of the nanotubes, gradually building them up—and preserving their structural chirality.
A Recipe For Cooking Up Carbon Nanotubes
The new breakthrough steps things up a notch toward commercialization. In the latest announcement from USC, the team discovered how to define the atomic structure of carbon nanotubes.
The definition or “growth recipe” is based on the fact that every particular type of carbon nanotube expands and contracts at a particular frequency, which can be observed though a spectroscopic technique. That enabled researcher to demonstrate a precise match of atomic structure between the newly grown nanotubes.
The new findings also fostered an understanding of the conditions needed to grow the nanotubes at different speeds and lengths.
Before we move along let’s note for the record (because we usually do) that we taxpayers can give ourselves a big group hug for the overall research effort. Along with the nonprofit industry research consortium Semiconductor Research Corporation and The Center on Functional Engineered Nano Architectonics at UCLA, funding for the project came from the Office of Naval Research and an interesting little arm of the Department of Defense called the Defense Threat Reduction Agency.
Many Paths To Low Cost Carbon Nanotubes
Of course the NIST/USC collaboration isn’t the only carbon nanotube game in town. One particularly intriguing example comes from MIT, which is currently working on low cost carbon nanotube sensors that can be fabricated by a technique very similar to drawing on paper with a lead pencil.
Speaking of graphene, for those of you new to the topic graphene is an arrangement of carbon atoms with a hexagonal structure like that of carbon nanotubes, only arranged in a one atom thick sheet instead of a tube. Discovered in 2004, graphene has engendered thousands of research papers for its unique properties of strength and conductivity.
Regular readers of CleanTechnica first saw graphene dubbed the “miracle material of the new millennium” back in June 2009 on this site. We’ve been following the research ever since with multiple writers contributing dozens of articles and we’re happy to report that PBS Newshour finally caught up to us just yesterday with a feature story on graphene, calling it (somewhat more lamely, we think) “the World’s New Wonder Material.”