Terahertz Dispersion Characteristics of Super-aligned Multi-walled Carbon Nanotubes and Enhanced Transmission through Subwavelength Apertures

Abstract

The terahertz (THz) dielectric properties of super-aligned multi-walled carbon nanotube (MWCNT) films were characterized in the frequency range from 0.1 to 2.5 THz with terahertz time-domain spectroscopy. The refractive index, effective permittivity, and conductivity were retrieved from the measured transmission spectra with THz incident wave polarized parallel and perpendicular to the orientation of carbon nanotubes (CNTs), and a high degree of polarization dependence was observed. The Drude-Lorentz model combined with Maxwell-Garnett effective medium theory was employed to explain the experimental results, revealing an obvious metallic behavior of the MWCNT films. Moreover, rectangular aperture arrays were patterned on the super-aligned MWCNT films with laser-machining techniques, and the transmission measurement demonstrated an extraordinarily enhanced transmission characteristic of the samples with incident wave polarized parallel to the orientation of the CNTs. Surface plasmon polaritons were employed to explain the extraordinarily enhanced transmission with high accuracy, and multi-order Fano profile was applied to model the transmission spectra. A high degree of agreement was exhibited among the experimental, numerical, and theoretical results.

Large graphene-induced shift of surface-plasmon resonances of gold films: Effective-medium theory for atomically thin materials

“…The theory becomes more important today as nanostructures and nanomaterials are routinely synthesized and assembled to make nanocomposites or metamaterials for the desired electromagnetic responses and functionalities. Because the original mixing formula is based on non-interacting spherical inclusions in a host medium, it has been revised to handle non-spherical inclusions with mutual interaction [3][4][5][6][7][8][9][10][11][12][13][14][15]. The original and revised mixing formulas have been proven to be powerful tools in accurately capturing the macroscopic electromagnetic responses of composite materials, and good agreements have been demonstrated between theory and experiment for many systems such as metal-ceramic films [6,16], polymer-ceramic composites [17], amorphous silicon thin films [18], polymer-single-walled carbon nanotube composite [8], and aligned carbon nanotube film [19,20].…”

Novel Terahertz Spectroscopy Analysis for the Electrode with Carbon Nanotubes (CNTs) in Lithium-Ion Batteries

“…THz-TDS was used to measure the THz signal transmitted through the cathode films and the bare silicon (as a reference). The frequency-domain output THz signals were obtained in time-domain THz signals using the Fourier transform analysis of the input and output time-domain THz signals [25][26][27][28].…”

Field focusing on carbon nanohorns

“…[8][9][10][11] A part of those reports exhibit negative values of the real part of the dielectric constants, particularly in the midand far-infrared regime, around 10 μm and longer. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] This negativity indicates a metallic and electrically conductive property of the carbon nanotubes. We consider that such a negative real part of the dielectric constant of carbon nanotubes can cause a large field focusing at the tip of the nanotubes, as an analogy with the cases of sharp metal tips.…”