| Project/Area Number |
22K18270
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| Research Category |
Grant-in-Aid for Challenging Research (Pioneering)
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| Allocation Type | Multi-year Fund |
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| Review Section |
Medium-sized Section 13:Condensed matter physics and related fields
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| Research Institution | Okinawa Institute of Science and Technology Graduate University |
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Principal Investigator |
Dani Keshav 沖縄科学技術大学院大学, フェムト秒分光法ユニット, 教授 (80630946)
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| Project Period (FY) |
2022-06-30 – 2025-03-31
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| Project Status |
Granted (Fiscal Year 2023)
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| Budget Amount *help |
¥25,740,000 (Direct Cost: ¥19,800,000、Indirect Cost: ¥5,940,000)
Fiscal Year 2024: ¥8,450,000 (Direct Cost: ¥6,500,000、Indirect Cost: ¥1,950,000)
Fiscal Year 2023: ¥8,710,000 (Direct Cost: ¥6,700,000、Indirect Cost: ¥2,010,000)
Fiscal Year 2022: ¥8,580,000 (Direct Cost: ¥6,600,000、Indirect Cost: ¥1,980,000)
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| Keywords | Extreme UV light source / High order / harmonic generation / XUV-PEEM / Nano-ARPES / Twisted 2D material / Moire pattern / Nano-APRES / Twisted 2D materials / Extreme Ultraviolet / Higher Harmonic / Angle resolved / photoemission / electron microscopy |
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| Outline of Research at the Start |
Creating new sources of light with non-standard wavelengths can provide powerful tools for science and technology. The XUV region of the electromagnetic spectrum creates new opportunities in photoemission spectroscopy like the powerful technique of Angle Resolved Photoemission Spectroscopy, and industrial fields like semiconductor fabrication. We propose to build a novel table-top source of XUV radiation that will provide significantly higher flux densities, to further push the boundaries of ARPES techniques and to study the newly emerging two-dimensional semiconductor heterostructures.
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| Outline of Annual Research Achievements |
The goal of this Kakenhi proposal is to develop a table-top XUV photon source with sufficient photon flux to enable time-, angle-, spectral-, and momentum-resolved photoemission spectroscopies with nanoscale spatial resolution. This fiscal year, we have continued to explore various methods to enhance photon flux. We discovered that meticulous gas management in and after the gas plasma interaction region is crucial for this improvement. Utilizing our XUV photon sources, we conducted several experiments using the photoemission microscope. Specifically, we examined and analyzed defects and electronic structures in hBN ferroelectric samples. Furthermore, we applied our XUV-PEEM technique to investigate the origin of mid-gap states in polycrystalline perovskite thin films. Additionally, we have started testing the beamline on a momentum microscope, which will be capable of performing TR-XUV-nano-ARPES.
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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 objectives of this research are: (A) to develop an XUV light source with photon flux density orders of magnitude higher than currently available; (B) to utilize this new light source for time-resolved PEEM and nano-ARPES measurements; and (C) to explore moire; structures and their excitons in 2D heterostructures. Up to now, we have made significant progress in all areas. Below is a summary of our achievements:
(A) Our XUV light source has achieved a spot size of 32 x 7 um and a flux density of up to 4 x 10^18 photons/sec/ cm^2, which is two orders of magnitude better than our previous light source (1 x 10^16 photons/sec/cm^2). In addition to optimizing phase matching and laser parameters, we found that effective gas management at and immediately following the gas plasma interaction region is crucial for improving photon flux.
(B) We have successfully performed XUV-PEEM with a spatial resolution better than 100 nm. We are now working on coupling the light source with a momentum microscope to conduct micro/nano-ARPES experiments.
(C) We have investigated defects and ferroelectric domain structures in twisted 2D materials and are currently writing up this manuscript. Additionally, we conducted experiments to study mid-gap defects in perovskite thin films using this XUV light source.
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| Strategy for Future Research Activity |
This year, we will continue to make progress on our three objectives:
(A) To further optimize the flux density of our XUV light source, we plan to investigate phase matching conditions under varying gas jet diameters, gas pressures, and laser fluences. Additionally, we intend to invest in an improved motorization setup and a new ellipsoidal mirror, which should help us achieve higher flux density.
(B) We will optimize and couple the XUV light source with a momentum microscope, which offers better energy resolution than the PEEM system we used previously. This enhancement will enable high-resolution TR-XUV-nano-ARPES experiments.
(C) With the new TR-XUV-nano-ARPES setup in place, we will focus on studying moire-localized excitons in various 2D heterostructures.
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