2020 Fiscal Year Research-status Report
Optical and Optoelectronic Studies of Boron Nitride Nanotube/Carbon Nanotube Coaxial Heterostructures
| Project/Area Number |
20K15121
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| Research Institution | Institute of Physical and Chemical Research |
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Principal Investigator |
李 臻 国立研究開発法人理化学研究所, 光量子工学研究センター, 特別研究員 (20869359)
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| Project Period (FY) |
2020-04-01 – 2022-03-31
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| Keywords | carbon nanotubes / boron nitride nanotubes / heterostructures / excitons / photoluminescence |
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| Outline of Annual Research Achievements |
Single-walled carbon nanotubes were synthesized on location-tagged transmission electron microscope grids and subsequently coated by boron nitride by chemical vapor deposition. Different numbers of boron nitride shells were formed on the carbon nanotubes by controlling the coating duration. Photoluminescence excitation spectroscopy and photoluminescence imaging were performed before and after boron nitride coating on the same carbon nanotubes in order to compare the excitonic energy shifts as well as visualize the carbon nanotube shape. Different number of boron nitride shells introduced different strengths of dielectric screening to the excitons in the carbon nanotubes and the excitonic energies showed quantized redshifts as a result. The redshifts induced by dielectric screening from thick boron nitride shells were comparable to that induced by two-dimensional boron nitride transferred onto air-suspended carbon nanotubes. Additionally, strains due to boron nitride coating contributed to occasional blueshifts of the excitonic energies. Transmission electron microscopy was then attempted to quantify the actual number of boron nitride shells on the carbon nanotubes that had been optically characterized. A correlation between the excitonic energy shifts and the boron nitride shell number was expected.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
So far the results are within our expectation, and we are making progress according to the first subproject of our proposed research. The excitonic energy shifts of the carbon nanotubes induced by BN coating are roughly correlated with the BN shell number, although the strains introduced by BN create some complexity, which is also expected. TEM will be used to quantify the BN shell number, and a strain model might be needed to elucidate the relationship between the excitonic energy shift, dielectric screening from BN and the strain effect introduced by BN coating.
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| Strategy for Future Research Activity |
More high-resolution TEM characterizations will be performed to quantify the BN shell number, and the relationship between the excitonic energy shift and the BN shell number will be understood. From the relationship we will be able to propose a nondestructive method to quantify the BN shell number in these 1D heterostructures by only using photoluminescence excitation spectroscopy. Then we will explore the intrinsic defect states in these BN shells by using a different excitation energy. Efforts will be made to study the interaction between such intrinsic defect states and the excitonic states in the carbon nanotubes.
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| Causes of Carryover |
Due to the COVID-19 pandemic, conferences were either cancelled or held online, travel expenses were zero. During the state of emergency, we had to work remotely from home, usage of equipment including cleanroom tools, SEM and TEM was limited, and article costs were much less due to inaccessibility to the laboratory.
We plan to spend the fund on articles, equipment usage and travel if possible when things come back to normal in next fiscal year. TEM will be extensively used to explore the BN shell number dependence of the exitonic energy shifts.
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