Thickness Dependency of Carbon Nanotube Thin Films' Opto-Plasmonic Properties

Thin films with a thickness of a few nanometers to a few tens of nanometers, also called trans-dimensional (TD) materials, are an exceptional tool to tune various opto-plasmonic properties of a system that are unattainable when using both single-layered two-dimensional (2D) counterparts and/or three-dimensional (3D) bulk counterparts. Taking the planned periodic arrangement of single-walled carbon nanotube (SWCNT) films as an example, we semi-analytically calculate the dynamical conductivities and dielectric responses of a TD film as a function of the photon frequency and radius of the SWCNT. The periodic array of SWCNs has an anisotropic dielectric response, which is almost a constant and is the same as that of the host dielectric medium in the perpendicular direction of the alignment of the SWCNT array due to the depolarization effect that SWCNTs have. However, the dielectric response depends on the incident photon energy, in addition to the film’s thickness, the SWCN’s sparseness, inhomogeneity, and the SWCNT’s diameter. The energy difference between the resonant absorption peak and the plasmonic peak varies with the thickness of the film. We reveal that thinner SWCNT TD films have a comparatively stronger exciton-plasmon coupling than thicker SWCNT TD films.

The author gratefully acknowledges the support of the 2024 Ralph E. Powe Junior Faculty Enhancement Awards, provided by Oak Ridge Associated Universities (ORAU).