Surface Plasmon Resonance Excited by Super-aligned Multi-walled Carbon Nanotube Film Metasurfaces

Surface plasmon polaritons (SPPs) excited by the resonance interaction between the free electrons of the conductor and the electromagnetic field of the light play an important role in metamaterials. Here, we experimentally demonstrate the subwavelength, terahertz (THz) metasurfaces based on super-aligned multi-walled carbon nanotubes (MWCNT) film can support SPPs. The MWCNT film was prepared by drawing out from the super-aligned MWCNT arrays and then was transferred onto a silicon substrate. After that, periodic array structures were etched on the MWCNT films by a laser-machining technique to prepare MWCNT metasurfaces. The dielectric properties of the unetched MWCNT film were studied in detail in frequency range from 0.2 to 2.5 THz. The real part of the effective permittivity retrieved from the measured transmission spectra is negative, which is a critical condition to support propagating SPPs. The Drude-Lorentz model combined with Maxwell-Garnett effective medium theory was used to explain the measured results, which reveals an obvious metallic behavior of the MWCNT films. Obvious enhanced resonant peaks of transmission spectra of the MWCNT metasurfaces are observed experimentally, which are attributed to the surface plasmon polariton resonance. Furthermore, the surface plasmon resonance based on super-aligned MWCNT metasurfaces has been experimentally demonstrated to be applied for analytes sensing, showing the lowest detection mass of 10 ng and the sensitivities of 2.0 × 10⁻³/ppm.