Carbon nanotube transistors outperform silicon

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University of Wisconsin-Madison materials engineers claim to have created carbon nanotube transistors that achieve currents 1.9 times higher than silicon transistors.

"This achievement has been a dream of nanotechnology for the last 20 years," said Professor Michael Arnold. " There has been a lot of hype about carbon nanotubes that hasn't been realised, and that has kind of soured many people's outlook. But we think the hype is deserved. It has just taken decades of work for the materials science to catch up and allow us to effectively harness these materials.

"This breakthrough in carbon nanotube transistor performance is a critical advance toward exploiting carbon nanotubes in logic, high-speed communications, and other semiconductor electronics technologies."

According to the researchers, carbon nanotube transistors should be able to perform five times faster or use five times less energy than silicon transistors. The nanotube's small dimension makes it possible to rapidly change a current signal travelling across it, which could lead to substantial gains in the bandwidth of wireless communications devices.

Carbon nanotubes have long been recognised as a promising material for next-generation transistors. However, researchers have struggled to isolate purely carbon nanotubes, which are crucial, because metallic nanotube impurities act like copper wires and disrupt their semiconducting properties.

The UW-Madison team used polymers to get rid of metallic nanotubes, achieving a solution of high-purity semiconducting carbon nanotubes with less than 0.01% of metallic nanotubes.

The polymer the UW-Madison researchers used to isolate the semiconducting nanotubes also acted like an insulating layer between the nanotubes and the electrodes, impeding good electrical contact, so the team ‘baked’ the nanotube arrays in a vacuum oven to remove the insulating layer.

Work is underway to develop high performance radio frequency amplifiers that could boost a cell phone signal.