2020 Fiscal Year Research-status Report
Chirality engineering of single-walled carbon nanotubes by in situ TEM probing
| Project/Area Number |
20K05281
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| Research Institution | National Institute for Materials Science |
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Principal Investigator |
湯 代明 国立研究開発法人物質・材料研究機構, 国際ナノアーキテクトニクス研究拠点, 主任研究員 (50646271)
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| Project Period (FY) |
2020-04-01 – 2023-03-31
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| Keywords | Carbon nanotubes / Chirality / Electron microscopy / Machine learning |
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| Outline of Annual Research Achievements |
Carbon nanotubes (CNTs) are one-dimensional tubular structures composed of single sheets of graphene and have exceptional electrical, mechanical, and thermal properties. Carbon nanotubes have a helical structure where the chirality determines them to be metallic or semiconducting. Semiconducting CNTs are promising in nanotransistors. Currently, the lack of chirality control hinders the practical applications. This project aims to understand the formation and transformation mechanism of CNT chirality using in situ electron microscopy.
This year, the chiral transition condition under mechanical strain and Joule heating was optimized by programming the movement and bias of STM probes inside a TEM. And the critical conditions for initialing the chiral transitions were established. The transition processes were analyzed by electron diffraction. A surprisingly clear transition pattern was discovered by fine control of the multiple steps. In addition to transformation mechanism, in situ TEM growth and machine learning was introduced to analyze the formation mechanism of the CNT structure. A method of precisely determining the phase structure of the catalyst was established. And the correlation between the growth conditions and the crystalline structure of the CNTs was established by modeling the relation using machine learning method. The random forest regression model showed the highest performance, was able to predict growth conditions for high quality CNTs.
These achievements paved the way for precise control of the CNT structures for their applications in nanoelectronics.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
The plan and goal for this year is to establish the critical conditions for SWCNTs’ chirality transitions. By developing a LabVIEW based program to control the movement and bias of the STM probes and using electrical measurement result as a feedback control signal, the critical transition conditions, and multiple chiral transitions of individual CNTs have been achieved. Up to 29 times of transitions have been recorded by in situ electron diffraction. In addition, a surprising transition pattern was revealed and there is a clear trend for the chiral angles to increase.
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| Strategy for Future Research Activity |
The chirality transition mechanism will be clarified by analyzing the changes of chiral indices and by theoretical calculations. Based on the chirality transitions, by using a transistor configuration to measure the electrical properties, controllable metal-to-semiconductor transition will be the main goal for the next step. In addition, high performance transistors using the chirality transformed semiconducting nanotube as a channel will be fabricated to investigate the short channel effects and contact effects for the transistors with the channel length down to 10 nanometers.
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| Causes of Carryover |
The budget will be mainly used for the in situ TEM machine time, for targeted controllable metal-to-semiconductor transition by programmed chirality transitions and for fabricating transistors using the chirality transformed nanotube as a semiconducting channel.
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