As devices continue to be built on an increasingly small scale, scientists are looking toward developing ways to engineer materials at the atomic level. In a breakthrough that will contribute to this, published in Nature Communications, researchers from the RIKEN Cluster for Pioneering Research and RIKEN Center for Advanced Photonics, along with collaborators, have developed a way to use a "dry transfer technique" -- a technique that uses no solvent -- to position optical quality carbon nanotubes in a precise way.1

To solve this issue, the researchers looked for a way to engineer the nanotubes without using solvents. They experimented with using anthracene, a chemical derived from oil, as a sacrificial material. Essentially, they picked up the nanotube on a scaffolding of anthracene to carry it wherever they wanted, and then used heat to sublimate the anthracene, leaving the nanotube in an optically pristine condition. They also developed a method for monitoring the photoluminescence of the nanotubes during the transfer, ensuring that a nanotube with the desired optical properties would be placed at a right location.


  • 1. Carbon nanotubes are a promising type of materials with potential uses in applications such as light-emitting diodes, single-electron transistors, or as single photon sources. They are essentially tubes made up of graphene twisted in specific ways, and the way they are twisted is critical for allowing the desired properties to emerge. Creating devices with desired properties requires precise manipulation of the position and orientation of the nanotubes, along with a property known as "chirality," which essentially describes how much it is twisted. It is difficult to manipulate the molecules precisely, however, as using solvents or high-temperature treatment inevitably leaves the nanotubes dirty, hampering their optical characteristics.

Keigo Otsuka, Nan Fang, Daiki Yamashita, Takashi Taniguchi, Kenji Watanabe, Yuichiro K. Kato. Deterministic transfer of optical-quality carbon nanotubes for atomically defined technologyNature Communications, 2021; 12 (1) DOI: 10.1038/s41467-021-23413-4

When continued device scaling reaches the ultimate limit imposed by atoms, technology based on atomically precise structures is expected to emerge. Device fabrication will then require building blocks with identified atomic arrangements and assembly of the components without contamination. Here we report on a versatile dry transfer technique for deterministic placement of optical-quality carbon nanotubes. Single-crystalline anthracene is used as a medium which readily sublimes by mild heating, leaving behind clean nanotubes and thus enabling bright photoluminescence. We are able to position nanotubes of a desired chirality with a sub-micron accuracy under in-situ optical monitoring, thereby demonstrating deterministic coupling of a nanotube to a photonic crystal nanobeam cavity. A cross junction structure is also designed and constructed by repeating the nanotube transfer, where intertube exciton transfer is observed. Our results represent an important step towards development of devices consisting of atomically precise components and interfaces.