| 研究課題/領域番号 |
21K04874
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| 研究種目 |
基盤研究(C)
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| 配分区分 | 基金 |
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| 応募区分 | 一般 |
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| 審査区分 |
小区分29020:薄膜および表面界面物性関連
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| 研究機関 | 東京大学 |
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研究代表者 |
林 冠廷 東京大学, 生産技術研究所, 特任研究員 (70772309)
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| 研究期間 (年度) |
2024-01-17 – 2025-03-31
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| 研究課題ステータス |
交付 (2024年度)
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| 配分額 *注記 |
4,030千円 (直接経費: 3,100千円、間接経費: 930千円)
2023年度: 1,040千円 (直接経費: 800千円、間接経費: 240千円)
2022年度: 1,690千円 (直接経費: 1,300千円、間接経費: 390千円)
2021年度: 1,300千円 (直接経費: 1,000千円、間接経費: 300千円)
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| キーワード | 近接場光学顕微技術 / THz顕微技術 / ナノ熱計測 / 近接場顕微技術 / THz光学系 / ナノサーモグラフィー |
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| 研究開始時の研究の概要 |
To improve the SNR of passive THz s-SNOM, reducing the huge background radiation is one of the solutions. The main source of the background radiation is the 300 K plank radiation from samples and environment. Therefore, cooling down the optics and scanning probe microscope to 4.2 K is an efficient method to reduce Plank radiation in THz region. The THz near-field signal excited in non-equilibrium state is expected to be easily extracted, and the SNR will be improved. The low-temperature THz s-SNOM is expected to study the energy dissipation in device and mesoscopic transport in novel material.
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| 研究実績の概要 |
To improve the spatial resolution of far-field (FF) images of low-temperature THz s-SNOM, I’ve designed a new confocal optics. The new design uses germanium (Ge) meniscus lens design for objective and relay lens to reduce spherical aberration. The Ge meniscus objective has a numerical aperture of 0.35 and a working distance of 12 mm. A pinhole of 60 μm diameter is placed between the objective and the relay lens. To check the focal spot size of the confocal optics, the LWIR FF thermal signals are measured at the boundary between Au and SiO2. The spatial resolution of the FF signals is estimated to be ~70 μm, better than the 110 μm obtained from the single lens optics. Further, to reduce the acquisition time, the tip-modulation method is applied to reduce the extra background radiation induced by the sample-height modulation method. With these two improvements, the acquisition time of near-field (NF) detection in the low-temperature THz s-SNOM is improved to 3 s from 10 s.
An NF signal is successfully detected on the NiCr/SiO2 sample with a 3 s integration time by using. According to the NF decay data, the NF signals observed on the NiCr can be explained by the electromagnetic evanescent fields induced by the thermal random motion of the conduction electrons.
The submicron-structure metallic and graphene device has been fabricated by e-beam lithography. The current-induced NF is detected for the first trial by using the room-temperature s-SNOM.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
Proceeding as planned, I've completed the improvement step of the signal-to-noise ratio of the near-field signal for low-temperature THz s-SNOM. Further, I've establish the e-beam lithography process for the metallic and graphene nano-device. The electrotransport measurement system for biasing the nano-device is set up in room-temperature s-SNOM. The far-field signal of the biasing device is obtained successfully， and the near-field detection is executing. After the near-field experiment with room temperature THz s-SNOM, the devices will be moved into the 4.2 K THz s-SNOM.
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| 今後の研究の推進方策 |
The remaining two years, I plan to improve the fabrication process to increase the survival rate after adding the bias current or cooling down to 4.2 K chamber. The defect rate of the graphene device is still high. The device easily broken after adding bias current or cooling down to 4.2 K chamber. The fabricated metal and graphene device will be first examined with the room temperature THz s-SNOM to make sure that the device work well. Then, I will move the device into the 4.2 K THz s-SNOM to image the excess current-induced excess noise fields. This result could reveal the mechanism of the energy loss of the non-equilibrium electrons, and will be compared to the results measured at room temperature.
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