Carbon nanotubes move closer to competing with silicon

Carbon nanotube circuits

An international team based at Stanford has reached an important milestone in pursuit of faster computing: It can now create stable carbon nanotube transistors that are as small as the best silicon transistors.

The transistors measure just 20 nanometers across, compared to the 22 nanometer silicon transistors found in Intel’s advanced devices. The team announced its work in the March issue of ACS Nano.

For decades, silicon-based computer chips have dominated the electronics industry. But a new class of materials that includes graphene and carbon nanotubes is threatening to upset silicon’s dominance by potentially offering faster and more efficient computing. Graphene is made of an atom-thick sheet of carbon atoms, and carbon nanotubes are rolled-up graphene. If researchers improve their stability at tiny scales, they could eventually create transistors that measure just one or a few atoms across–far smaller than a silicon transistor could ever be. And smaller transistors means more can fit on a chip, leading to even faster computing.

Scientists are actually already able to make carbon nanotube transistors that measure just 1 nanometer across. But it is very difficult to manufacture them precisely in batches large enough to incorporate into a chip. As a result, research has focused on creating larger, stable carbon nanotube transistors and gradually bringing their size down. Last year, the same Stanford team created a computer with 142 carbon nanotube transistors that measured 100 nanometers across.

The new, smaller transistors operate 100 times faster and use 99.5 percent less power than the nanotube transistors made last year. The team grew them in a high-temperature oven–a common manufacturing technique–with an unusual addition: quartz. Quartz is a crystal, which means its structure is a repeating pattern. The pattern kept the nanotubes orderly and parallel. The team also weeded out the roughly third of the carbon nanotubes that were unusable.

But they are still not as powerful or fast as silicon transistors, according to Chemical & Engineering News. To achieve similar performance to silicon, the Stanford team will need to construct each transistor out of more tightly packed carbon nanotubes.

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