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Title: Terahertz Transmission Ellipsometry of Vertically-Aligned Multi-Walled Carbon Nanotubes
Abstract: We demonstrate time-resolved terahertz transmission ellipsometry of vertically-aligned multi-walled carbon nanotubes. The angle-resolved transmission measurements reveal anisotropic characteristics of the terahertz electrodynamics in multi-walled carbon nanotubes. The anisotropy is, however, unexpectedly weak: the ratio of the tube-axis conductivity to the transverse conductivity is merely 2.3, which is constant over the broad spectral range of 0.4-1.6 THz. The relatively weak anisotropy and the strong transverse electrical conduction indicate that THz fields readily induce electron transport between adjacent shells within multi-walled carbon nanotubes.
Title: Terahertz Imaging of Inhomogeneous Electrodynamics in Single-Layer Graphene Embedded in Dielectrics
Abstract: We investigate electron transport properties in large-area, single-layer graphenes embedded in dielectric media, using free-space THz imaging and time-domain spectroscopy. Two different types of graphene layer, sandwitched by a thin PMMA layer and a Si substrate, exhibit distinctive spatial inhomogeneity of sheet conductivity. The non-contacting, non-destructive THz probe reveals that the PMMA layer induces a small, yet noticeable reduction in conductivity.