2021 Fiscal Year Research-status Report
極低温THz近接場顕微鏡を用いた微小回路エネルギー散逸の観察
| Project/Area Number |
21K04874
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| Research Institution | The University of Tokyo |
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Principal Investigator |
林 冠廷 東京大学, 生産技術研究所, 特任助教 (70772309)
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| Project Period (FY) |
2021-04-01 – 2024-03-31
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| Keywords | 近接場光学顕微技術 / THz顕微技術 |
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| Outline of Annual Research Achievements |
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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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
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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| Strategy for Future Research Activity |
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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| Causes of Carryover |
The incurring amount will mainly be used to buy a voltage amplifier, made by Tabor Electronics Ltd., which costs about 700,000yen.
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Research Products
(7 results)
