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Electromagnetic absorbers based on ultra-thin metallic film are desirable for many applications such as plasmonics, metamaterials, and long-wavelength detectors. A metallic film will achieve a maximum 50% of electromagnetic wave absorption, frequency independent, at a thickness defined by its conductivity, typically in the sub-Angstrom range for good metals if bulk conductivity is maintained throughout. This makes it extremely difficult to obtain substantial absorption from thin metal films, in contrast to 2D materials such as graphene. Luckily, however, from a practical point of view, metal conductivity is drastically reduced as the film becomes sub-100 nm, to make it a race between the thinnest possible metal thickness experimentally achievable vs the conductivity reduction. Here, we demonstrate a near-50% absorption at a gold film thickness of 6.5 nm, with conductivity much reduced from the bulk value, down to the range of 106 Siemens per meter. Studying the effect of the substrate thickness, we found that the common cover glass, with its thickness much smaller than the wavelength, achieves symmetric absorption of 44%, implying that a pseudo-free-standing limit is achieved. Our work may find applications in infrared sensing as in bolometers and biomedical sensing using microwaves. [ABSTRACT FROM AUTHOR]

Nano-metamaterials designed to operate at a certain resonance frequency enhance the magnitude of terahertz (THz) wave transmission by three orders of magnitude or even more. In this pursuit, controlling magnitude of resonant transmission and tuning the resonance frequency is increasingly important for application in low power THz electronics and devices. THz optical properties of chemically doped poly(3,4‐ethylenedioxythiophene):poly(4‐styrenesulfonate) (PEDOT:PSS) have been studied, however its effect on the THz transmission properties in combination with nano-metamaterials have not yet been demonstrated. Here we demonstrate the efficient control over resonant THz transmission and tuning of resonance frequency of different nano-metamaterials using PEDOT:PSS, without any toxic chemical doping. By ease of simple solution processing with single step and drop-casting 10 μL aqueous solution of PEDOT:PSS on different nano-metamaterials with varied concentrations, we were able to dynamically control the THz transmission along with resonance frequency. This dynamic control of transmission and shift in resonance frequency can be attributed to improved conductivity of PEDOT:PSS and its interaction with strongly localized THz field of the metamaterial. [ABSTRACT FROM AUTHOR]

Hybrid composites have been prepared by solution processing method using various MWCNT concentrations in reduced graphene oxide/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (rGO-PEDOT:PSS) matrix. Structural and morphological characteristics of the prepared composite films have been characterized by X-ray diffraction, scanning electron microscopy, field emission scanning electron microscopy, Raman spectroscopy, UV-visible spectroscopy and Fourier transform infrared spectroscopy. The electrical transport measurement of composites conducted by four-point contacts shows increase in conductivity with MWCNT wt% in the composite system. The enhanced electrical conductivity as a result of improved dispersion of MWCNTs and rGO has been observed barely affecting the optical properties in the visible region. The observed improvement in electrical properties barely affecting its optical properties in the visible region can be attributed to synergistic effect of MWCNTs and rGO networks on the composite. This result suggests that such hybrid composite materials could be used as transparent conductor applications in optoelectronic devices. [ABSTRACT FROM AUTHOR]