Scientists have created the largest computer chip yet to be made from carbon nanotubes: rolled up sheets of atom-thick graphene that conduct electricity at super-fast speeds.
Some researchers hope to use carbon nanotubes in future computers because they conduct electricity faster and more efficiently than silicon does. Until now, engineers have increased the power and speed of ordinary silicon computer processors by shrinking the switches known as transistors, but these are reaching a fundamental limit.
The first carbon nanotube (CNT) computer, made in 20131, contained only hundreds of electronic switches known as transistors. The processor revealed this week in Nature2 has 14,000 transistors. “This work takes a big step forward and gets much closer to a commercial chip,” says Yanan Sun, a physicist at the Shanghai Jiao Tong University in China, who was not involved in the work.
A team at the Massachusetts Institute of Technology (MIT) in Cambridge created the 16-bit processor, which can operate on numbers represented by up to 16 binary digits. Called RV16X-NANO, the device is far from a modern central processing unit, but it executed a program that churned out the message: “Hello, world! I am RV16XNano, made from CNTs”.
To make the chip, the team overcame long-standing issues with using CNTs in electronics. The researchers’ tactics included clever circuit design to mitigate natural defects in the tubes that cause some to be metallic — which means that they don’t have the semiconducting properties needed to be transistors. The processor also integrated two different types of transistor that are essential for modern computer circuitry.
In theory, a CNT processor could be ten times more efficient than a silicon one by running around three times faster and using about one-third of the energy, says Max Shulaker, the MIT physicist who led the work. This processor is slower than silicon devices, but the prototype will improve, he says. “The most important thing is that all of these techniques are compatible with existing design tools and manufacturing facilities,” he adds.
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