Using a transmission electron microscope, a team of materials scientists led by the International Center for Materials Nanoarchitectonics in Japan and the Queensland University of Technology has created a carbon nanotube transistor that’s 25,000 smaller than the width of a human hair.

A designer view of a single-wall carbon nanotube intramolecular junction with metallic portions on left and right ends and a semiconductor ultrashort 3 nm channel in between. Image credit: Tang et al., doi: 10.1126/science.abi8884.

Transistors, which are used to switch and amplify electronic signals, are often called the building blocks of all electronic devices, including computers.

The computer industry has been focused on developing smaller and smaller transistors for decades, but faces the limitations of silicon.

In recent years, researchers have made significant steps in developing nanotransistors, which are so small that millions of them could fit onto the head of a pin.

“In this work, we have shown it is possible to control the electronic properties of an individual carbon nanotube,” said senior author Professor Dmitri Golberg, a researcher with the International Center for Materials Nanoarchitectonics at Japan’s National Institute for Materials Science and the Centre for Materials Science and School of Chemistry and Physics at the Queensland University of Technology.

In the research, Professor Golberg and his colleagues created a tiny transistor by simultaneously applying a force and low voltage which heated a carbon nanotube made up of a few layers until outer tube shells separate, leaving just a single-layer nanotube.

The heat and strain then changed the chirality of the nanotube, meaning the pattern in which the carbon atoms joined together to form the single-atomic layer of the nanotube wall was rearranged.

The result of the new structure connecting the carbon atoms was that the nanotube was transformed into a transistor.

“The research demonstrated the ability to manipulate the molecular properties of the nanotube to fabricated nanoscale electrical device,” said first author Dr. Dai-Ming Tang, a researcher with the International Centre for Materials Nanoarchitectonics at Japan’s National Institute for Materials Science.

“Semiconducting carbon nanotubes are promising for fabricating energy-efficient nanotransistors to build beyond-silicon microprocessors.”

“However, it remains a great challenge to control the chirality of individual carbon nanotubes, which uniquely determines the atomic geometry and electronic structure.”

“In this work, we designed and fabricated carbon nanotube intramolecular transistors by altering the local chirality of a metallic nanotube segment by heating and mechanical strain.”

“The research in demonstrating the fundamental science in creating the tiny transistor was a promising step towards building beyond-silicon microprocessors,” Professor Golberg said.

The team’s work was published in the journal Science.

Dai-Ming Tang et al. 2021. Semiconductor nanochannels in metallic carbon nanotubes by thermomechanical chirality alteration. Science 374 (6575): 1616-1620; doi: 10.1126/science.abi8884