Probing THz Evanescent Waves of Non-equilibrium Dynamics

2017 Fiscal Year Final Research Report

• Project/Area Number: 16K17517
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Thin film/Surface and interfacial physical properties
• Research Institution: The University of Tokyo
• Principal Investigator: Lin Kuan-Ting 東京大学, 生産技術研究所, 特任助教 (70772309)
• Project Period (FY): 2016-04-01 – 2018-03-31
• Keywords: Near-field microscopy / THz image / Noise image / Graphene / Current crowding effect

Outline of Final Research Achievements

Detecting non-equilibrium dynamics of charge carrier in nano-device has remained to be a challenge for decades. To solve this technical issue, we used a passive THz scattering-type scanning near-field microscope (SNOM) to realize the detection.
In the graphene device, we imaged excess noise by probing electromagnetic evanescent waves (~20 THz) near the surface. In the metallic device, we imaged thermally excited evanescent wave. According to the simulation, the near-field intensity is consistent with the simulation of the current density distribution. The detected hot-position is due to the current-crowding effect. In GaAs semiconductor device, the near-field signal extending out of the constriction region was detected in non-linear region. This result originates from energy dissipation of hot electron. To sum up, the THz SNOM is proved to be powerful equipment for studying carrier dynamics in nano-device and expected for application in device industry and novel material study.

Free Research Field

Terahertz microscopy