| 研究課題/領域番号 |
16K17517
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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, 特任助教 (70772309)
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| 研究期間 (年度) |
2016-04-01 – 2018-03-31
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| キーワード | Near-field microscopy / THz image / Graphene / Noise image |
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| 研究実績の概要 |
To prove the passive THz scattering-type scanning near-field optical microscope (s-SNOM) that can be a unique experimental tool for investigating the non-equilibrium dynamics system via probing electromagnetic evanescent waves, we first observed the current-induced evanescent waves on graphene device.
The electrotransport measurement system has been introduced into the sample stage of the AFM system, which enables us to apply the voltage/current bias to the device. To eliminate the thermally excited evanescent waves from the excess current-induced evanescent waves, I ceased modulating the tip-height to extract the near-field signals and established the current-modulation method.
After the measurement method was established, we successfully observed 2D near-field images on the biased graphene. The near-field signals generated on the sample surface can be seen as the current-induced excess noise, which is related to the fluctuating charge/current. In the narrow constricted graphene, we found that the noise fields strongly show up in the constricted region due to the higher current density and increase almost linearly with increasing current. The temperature rise in the narrow constriction can be explained by considering the carrier energy dissipation through inelastic carrier-carrier, carrier-phonon, and carrier-impurity interactions. This work was reported in the 64th JSAP Spring Meeting.
The THz s-SNOM thus has been proved to be a unique non-invasive experimental tool for investigating the noise field distribution via the near-field mapping not only for the graphene devices.
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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
The project is progressing smoothly. The design and fabrication of the graphene devices and metallic nano-wire devices were carried out. We successfully observed 2D near-field images on the biased graphene device. The passive s-SNOM thus has been proved to be a unique non-invasive experimental tool for investigating the noise field distribution. The GaAs 2DEG conducting channels are now undergoing fabricating. Planned experiments were also conducted. The first graphene THz image results have been submitted and will be presented at international conferences in 2017 (EP2DS-22 and IRMMW-THz 2017).
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| 今後の研究の推進方策 |
For the second year, I will continuously design and fabricate the new graphene device, GaAs 2DEG narrow conducting channel, and Pt nanowire device. The results, obtained in the first year, shows that the passive THz s-SNOM can be applied to the non-equilibrium system. Therefore, the GaAs 2DEG system and metallic nano-wire, proposed in the project, also have a chance to image the non-equilibrium charge/current induced evanescent waves and study the energy relaxation processes of the charge carriers. To simulate the electron-phonon relaxation process, we planed to use the COMSOL simulator. It may help us to distinguish the energy relaxation process of electron-phonon in the non-equilibrium system.
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| 次年度使用額が生じた理由 |
Because the fabrication process of the 2DEG conducting device has not been finished, some experimental items, such as high power DC voltage supply, have not been bought yet. I did not attend the oversea international conference in the first year.
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| 次年度使用額の使用計画 |
For feedback-controlled electromigration in the metallic nano-wire device, the highly precision source/measure unit will be purchased. For data simulation, I plan to buy the COMSOL simulator. Some consumable goods are still needed for the following experiments. The EP2DS international conference has already accepted our submission about the graphene results. Therefore, I will attend the conference hold at Penn State University, U.S.A, in July 2017.
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