Carbon nanotubes are beginning to head out of the laboratory and into the edges of reality, according to a team of IBM researchers who have been hard at work creating carbon nanotubes that will be the basis for the next generation of computer chips.
The latest breakthrough as scientists continue to refine the handling and construction of the carbon nanotubes is that 10,000 of the tiny structures have been manipulated to fit and operate on a single chip using standard semiconductor processes, according to IBM. This is reportedly the first time that such an accomplishment has been possible.
"Carbon nanotubes, borne out of chemistry, have largely been laboratory curiosities as far as microelectronic applications are concerned," Supratik Guha, director of physical sciences at IBM Research, said in a statement. "We are attempting the first steps toward a technology by fabricating carbon nanotube transistors within a conventional wafer-fabrication infrastructure."
The significance of this work is that it is showing that the promise of carbon nanotubes is being shown in reality, rather than just in laboratory theories, said Guha. "The motivation to work on carbon nanotube transistors is that at extremely small nanoscale dimensions, they outperform transistors made from any other material. However, there are challenges to address such as ultra- high purity of the carbon nanotubes and deliberate placement at the nanoscale. We have been making significant strides in both."
Today's computer chips are built of silicon, which has allowed excellent performance for decades. But as computer chips get increasingly faster and smaller, the physical limitations of making chips smaller using silicon is being approached, which is why scientists are looking for alternative materials to use in chip construction.
That's where carbon nanotubes have shown great promise, because they will allow further miniaturization of computing components and continued advances in chip performance for future microelectronics, according to IBM.
So far, nanotube technology has been research-based, without direct links to commercialization of the processes that create such structures. With IBM's latest accomplishment, however, the possibilities now exist so that the 10,000 nanotubes on one chip will be scalable to much higher levels, which will allow the creation of computer chips built from carbon. The findings were published Oct. 28 in the peer-reviewed journal, Nature Nanotechnology (purchase required for viewing).
One of the biggest benefits that carbon offers over silicon is that the tiny "switches" or electronic circuits that can be fashioned on the chips can be made much smaller, allowing them to be assembled more densely on a chip. More circuits mean greater performance and more performance means faster devices and computing.
The newly discovered chemical process that allows 10,000 nanotubes to be placed onto a single chip is based on ion-exchange chemistry that allows the controlled and precise placement of the structures onto a chip, according to an IBM spokeswoman.
"The process starts with carbon nanotubes mixed with a surfactant, a kind of soap that makes them soluble in water," according to IBM. "A substrate is comprised of two oxides with trenches made of chemically modified hafnium oxide (HfO2) and the rest of silicon oxide (SiO2). The substrate gets immersed in the carbon nanotube solution, and the nanotubes attach via a chemical bond to the HfO2 regions while the rest of the surface remains clean."
By continuing to refine the method, greater nanotube densities will be reachable, which will lead to the creation and commercialization of nanotube-based chips, researchers believe.
"It's a first step toward commercialization," the spokeswoman said. "It takes them out of the kitchen lab into a commercial fabrication lab."
The 10,000 nanotubes-per-square-centimeter milestone is important because that's the minimum number of circuits that are needed to begin testing the operations of a new chip, the spokeswoman said. About 1 billion circuits per square centimeter are required to make an integrated circuit, so more research is obviously still needed to reach that goal.
Scientists believe that by 2020, silicon will lose steam in terms of being able to continue to scale in the creation of faster, smaller chips, according to IBM. By 2017, researchers hope that the basic processes will be in place to begin transitioning to carbon.