| 研究実績の概要 |
After improving the confocal optics and introducing tip-height modulation in the low-temperature passive THz s-SNOM system, the acquisition time of near-field detection improved to 3 s from 10 s. The near-field signals observed on the NiCr can be explained by the electromagnetic evanescent fields induced by the thermal random motion of the conduction electrons.
To study the energy dissipation in graphene devices, a potential material for carbon-based electronic devices due to its ultrahigh electrical and thermal conductivity, I fabricated narrow constricted graphene devices using electron beam lithography. The CVD-grown monolayer graphene was transferred to a silica substrate. With the room-temperature passive THz s-SNOM, I measured the evanescent fields induced by excess current. The near-field signals strongly appeared in the narrow wire region with a 1 μm width. The electrons obtained large electrical energy in the narrow region due to the high electric field. The near-field signals on graphene belong to the current-induced thermal fluctuating EM evanescent fields due to the high current density, and can be explained by the fluctuation-dissipation theorem. Furthermore, a gradually diffusive thermal dissipation appears on the anode side of the wide graphene region, which is considered as an electron-phonon relaxation process.
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