A New Dry Transfer Technique Precisely Positions Optical Quality Carbon Nanotubes

One of the trends for electronic devices in all industries is for them to get smaller and smaller. As devices are increasingly built on a smaller scale, scientists and material researchers are always looking to develop new materials at the atomic level. Researchers from the RIKEN Cluster for Pioneering Research and Center for Advanced Photonics, along with other collaborators, have developed a new technique for engineering matter at the atomic level. The new technique is a dry transfer technique that uses no solvents and can precisely position optical quality carbon nanotubes.

Carbon nanotubes are a type of material with potential applications in a variety of scenarios, including light-emitting diodes, single-electron transistors, or a single-photon source. Carbon nanotubes are tubes made of graphing twisted in specific ways, and the way they are twisted is critical to creating the desired properties of the finished product. The ability to create devices with the desired properties requires extreme precision in manipulating the position and orientation of nanotubes.

Creating devices also requires a property known as "chirality," which describes how much the nanotubes are twisted. Manipulating molecules with precision is difficult because solvents or high-temperature treatments typically leave the nanotubes dirty, impacting their optical characteristics. To alleviate those issues, scientists have been looking for a way to engineer nanotubes without solvents.

Project researchers experimented using anthracene, which is a chemical derived from oil as a sacrificial material. The team picked up the nanotube on the scaffolding of anthracene to carry it in a position where they wanted. They then used heat to sublimate the anthracene leaving the nanotube optically pristine. Researchers also came up with a method to monitor the photoluminescence of nanotubes during the transfer to ensure a nanotube with the required optical properties was positioned in the correct location.

Scientists confirmed that after the dry transfer technique was performed, the remaining nanotubes had bright photoluminescence up to 5000 times as bright as the original molecule. That property makes them ideal for optical devices, and the group was able to precisely position a nanotube on top of a nanosized optical resonator, enhancing its light emission properties.