Observation of quantum transport at room temperature in a 2.8-nanometer CNT transistor

An international joint research team led by the National Institute for Materials Science (NIMS) has developed an in situ transmission electron microscopy (TEM) technique that can be used to precisely manipulate individual molecular structures. Using this technique, the team succeeded in fabricating carbon nanotube (CNT) intramolecular transistors by locally altering the CNT’s helical structure, thereby making a portion of it to undergo a metal-to-semiconductor transition in a controlled manner.

Semiconducting CNTs are promising as the channel material for energy-efficient nanotransistors which may be used to create microprocessors superior in performance to currently available silicon microprocessors. However, controlling the electronic properties of CNTs by precisely manipulating their helical structures has been a major challenge.

This joint research team succeeded for the first time in controllably manipulating CNTs’ electronic properties by locally altering their helical structures using heat and mechanical strain. Using this technique, the team was then able to fabricate CNT transistors by converting a portion of a metallic CNT into a semiconductor, where the semiconductor nanochannel was covalently bonded to the metallic CNT source and drain. The CNT transistors, with the channel as short as 2.8 nanometers in length (1 nm = one billionth of a meter), exhibited coherent quantum transport at room temperature — wave-like electron behavior usually observed only at extremely low temperature.

The molecular structure manipulation technique developed in this research may potentially be used to fabricate innovative nanoscale electronic devices. The team plans to use this technique to engineer material structures with atomic-level precision to fabricate electronic and quantum devices composed of individual atomic structures or molecules.

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This project was carried out by a team consisting of researchers from NIMS (Dai-Ming Tang, Ovidiu Cretu, Xin Zhou, Feng-Chun Hsia, Naoyuki Kawamoto, Masanori Mitome, Yoshihiro Nemoto, Fumihiko Uesugi and Masaki Takeguchi), AIST (Don N. Futaba and Guohai Chen), University of Tokyo (Shigeo Maruyama, Rong Xiang and Yongjia Zheng), National University of Science and Technology, Russia (Sergey V. Erohin and Pavel B. Sorokin), N. M. Emanuel Institute of Biochemical Physics, Russia (Victor A. Demin and Dmitry G. Kvashnin), Shenyang National Laboratory for Materials Science, China (Song Jiang, Lili Zhang, Peng-Xiang Hou, Hui-Ming Cheng and Chang Liu), University of Wollongong, Australia (Yoshio Bando) and Queensland University of Technology, Australia (Dmitri Golberg (also Guest Researcher, International Center for Materials Nanoarchitectonics, NIMS)). Part of this work was supported by the JSPS Grant-in-Aid for Scientific Research and the JST Strategic Basic Research Program CREST.

This research was published in the online version of Science, a US scientific journal, on December 24, 2021, Japan Time (science.org/doi/10.1126/science.abi8884).