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Carbon Nanotubes Outperform Copper Nanowires as Interconnects

4/7/2008

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.

To better understand and more precisely measure the key characteristics of both copper nanowires and carbon nanotube bundles, the researchers used advanced quantum-mechanical computer modeling to run vast simulations on a high-powered supercomputer. It is the first such study to examine copper nanowire using quantum mechanics rather than empirical laws.

After crunching numbers for months with the help of Rensselaer’s Computational Center for Nanotechnology Innovations, the most powerful university-based supercomputer in the world, the research team concluded that the carbon nanotube bundles boasted a much smaller electrical resistance than the copper nanowires. This lower resistance suggests carbon nanotube bundles would therefore be better suited for interconnect applications.

“With this study, we have provided a road map for accurately comparing the performance of copper wire and carbon nanotube wire,” said Saroj Nayak, an associate professor in Rensselaer’s Department of Department of Physics, Applied Physics, and Astronomy, who led the research team. “Given the data we collected, we believe that carbon nanotubes at 45 nanometers will outperform copper nanowire.”

Because of the nanoscale size of interconnects, they are subject to quantum phenomena that are not apparent and not visible at the macroscale, Nayak said. Empirical and semi-classical laws cannot account for such phenomena that take place on the atomic and subatomic level, and, as a result, models and simulations based on those models cannot be used to accurately predict the behavior and performance of copper nanowire. Using quantum mechanics, which deals with physics at the atomic level, is more difficult but allows for a fuller, more accurate model.

Nayak said there are still many challenges to overcome before mass-produced carbon nanotube interconnects can be realized. There are still issues concerning the cost of efficiency of creating bulk carbon nanotubes, and growing nanotubes that are solely metallic rather than their current state being of partially metallic and partially semiconductor. More study will also be required, he said, to model and simulate the effects of imperfections in carbon nanotubes on the electrical resistance, contact resistance, capacitance, and other vital characteristics of a nanotube interconnect. Funding for this project was provided by the New York State Interconnect Focus Center.