Nanotubes caused a splash when they were first synthesized, following Nobel-winning work on ‘buckyballs’ — the spheres of 60 carbon atoms formally known as buckminsterfullerenes. The tiny carbon tubes promised smaller, faster circuits for more powerful computing. But making and controlling them is tricky.
For the past decade, Charles Lieber, a chemist at Harvard University, and his colleagues have been pursuing a nano-alternative: small wires made of crystals. These are more easily assembled into electrical circuits than nanotubes — although they aren't such good conductors. Lieber and his prolific team first synthesized nanowires in the late 1990s; this week they reveal their high-performance nanowire transistor. Lieber discusses the state of his art with Nature.
You've published a lot of high-profile papers. Any secret to your productivity?
I don't think there is a ‘secret’. Productivity stems from my motivation to produce research that will impact society in a positive way. I always ask myself, “Why is this important rather than simply interesting?”
What's the difference between using nanowires and nanotubes?
Semiconducting carbon nanotubes can possess perfect molecular structure. But this perfection does not readily allow for the variations in composition needed to support new functions. Nanowires have an advantage because their diameter can be easily varied, which means we can build devices that use substantially larger currents. Also, nanowires can be assembled so that they all behave the same way electronically, and this allows us to create multi-nanowire devices and complex circuits.
So, which is better?
It's not a question of proving something is better. We want to define the limits of nanowires, push them as far as we can and find real applications. There's room for many different types of nanostructures in the future. As long as people focus honestly on the science, things will progress naturally — although I do feel some are too narrowly focused on nanotubes.
How does your paper strengthen the argument in favour of nanowires?
Our work is state-of-the-art. We cannot yet judge whether nanowires will become the next microelectronics technology, because so many other issues need to be resolved — such as manufacturing and economics. But we have shown that nanowires are a viable alternative to silicon chips and nanotubes. Now we're focusing on the next big questions.