2020 Fiscal Year Research-status Report
Exciton physics in 1D-2D heterostructures
| Project/Area Number |
19K23593
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| Research Institution | Institute of Physical and Chemical Research |
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Principal Investigator |
Fang Nan 国立研究開発法人理化学研究所, 開拓研究本部, 基礎科学特別研究員 (50850509)
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| Project Period (FY) |
2019-08-30 – 2022-03-31
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| Keywords | carbon nanotubes / 2D materials / heterostructure / excitons |
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| Outline of Annual Research Achievements |
1) The interaction between h-BN substrate and CNTs has been clarified. The paper regarding h-BN/CNTs heterostructures has been published. The 2D transfer system has been set up, and a new transfer method based on anthracene crystals has been developed to form suspended 2D structures. Interaction between anthracene crystals and 2D materials has been investigated, indicating that 2D materials with many mobile carriers are more difficult to be picked up. This new transfer method enables us to prepare the suspended materials on top of any substrates. The strain is also suppressed, which is characterized by Raman spectroscopy. The interesting phenomena have been observed by forming nanoribbon 2D/CNT heterostructures, coming from the local dielectric effect on CNTs. Thickness dependence of WSe2 from monolayer to three layers has also been investigated. The quenching effect seems quite dependent on the layer number of WSe2, which has effect on the k-momentum states in carbon nanotubes.
2) 2D materials/cavity interaction. A large modulation of cavity mode by 2D materials has been observed. Different 2D materials show different cavity modulation ability, coming from different dielectric constant. The thickness dependence of cavity mode modulation has been investigated for both h-BN and WSe2. Difference between dielectric mode and air mode has been studied, indicating the importance of appropriate design of the cavity for achieving the large modulation by 2D materials. Quantized shift of the cavity mode has been observed due to the natural ultra-thin thickness of 2D materials.
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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
The research project has been going well as expected in this fiscal year. The new transfer method of 2D materials based on anthracene crystals has been developed, and makes is possible to prepare many new suspended 2D heterostructures. This transfer method brings out more interesting experiments in two main projects. The first one is the interaction between 2D materials and CNTs. Thickness dependence of 2D materials help clarify the origin of quenching effect. The second one is 2D materials/cavity interaction. Large mode modulation has been observed by transferring 2D materials on top of the cavity. I got trained in AFM and SSPD. I also studied the fundamentals of optics and cavities, which enables me to set up and change the optical system for different research purposes.
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| Strategy for Future Research Activity |
The following two main research projects will be focused on in the next fiscal year.
1) 2D/CNT heterostructures. The thickness dependence of WSe2 (from monolayer to bulk) will be investigated in WSe2/(9,7) CNT heterostructures. The diameter of the exciton will be experimentally clarified. Time-resolved PL will be performed to study the exciton dynamics further. The split of the main peak to two subpeaks are expected in the WSe2 nanoribbon/CNT heterostructures. The single photon emission is expected in this structure by decreasing WSe2 nanoribbon width.
2) 2D/cavity heterostructures. The thickness dependence of h-BN as well as WSe2 (from monolayer to bulk) will be investigated. Multi-transfer of WSe2 and h-BN will be performed on the cavity. Strain effect on cavity mode will be investigated.
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| Causes of Carryover |
Many conferences such as SSDM(International conference on solid state devices and materials) and APS march meeting have been changed to online due to COVID-19. In order to increase the remote work and decrease the infection risk, more optical measurements has been done at home remotely instead of sample preparation in the laboratory. Also the nano-fabrication process is reduced because it is done at Takeda cleanroom in the University of Tokyo. The development of new transfer 2D materials decreases the usage of 2D materials, which also decreases the usage for the amount.
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