Frequency dependencies and scattering diagrams of combined metal-dielectric surfaces in frequency range of 16–25 GHz

Background and Objectives: It is known that the design of attenuating coatings is usually based on two main physical principles: scattering and absorption. The absorbing coatings include ultrathin films, which at nanoscale thicknesses of the conductive layer absorb up to 50$\%$ of the incident electromagnetic energy, and are also capable of attenuating the signal in a wide frequency range due to frequency-independent properties. One of the ways to achieve high scattering readings is the use of metastructural coatings. This work aims to develop compact scattering materials that are a combination of planar metastructures with thin nanoscale films. Combining metastructures and thin absorbing nanofilms allows utilizing the advantages of both approaches, providing high efficiency of attenuation of electromagnetic waves in the microwave range. This opens up new opportunities for the creation of multifunctional and highly efficient attenuation coatings, which can find wide application in various industries and science. Materials and Methods: Metastructures are a set of specially arranged subwavelength metallic or dielectric structures that interact resonantly with the electric or magnetic components of incident electromagnetic waves. The electromagnetic properties of such structures are mainly determined by the characteristics of the resonators and their mutual arrangement. Such a construction principle allows them to exhibit an effective electromagnetic response, which is unattainable in natural materials. As a source of ohmic losses, thin films based on metallic, carbon and organic structures have been investigated in this work. Thin film materials used in combination with metastructures were a glass or sital substrate with a functional layer deposited on them via magnetron sputtering. Due to the island structure formed at a certain thickness of the conducting material, such films allowed absorbing up to 35$\%$ of the incident radiation. Glass-textolite with one-sided copper metallization was used as a material for obtaining the tested structures. The topology of the conductive structure was formed by milling. Results: The research results have demonstrated that the magnitude of the normal component of the reflected electromagnetic wave is significantly reduced at a resonant frequency of 18.8 GHz due to the use of combination of these attenuating coatings. At this frequency, the attenuation coefficient reaches its peak value of 97.8$\%$ of the incident wave. The width of this resonant peak, at which the attenuation of the wave reaches at least 70$\%$, is 450 MHz. But it should also be noted that the addition of a resistive film has the property of shifting the resonant peaks to a higher frequency region. Conclusion: Such materials can be used as protective coatings for buildings and structures in order to reduce the level of the passed electromagnetic radiation, but with a low reflection coefficient in the frequency range of 16–25 GHz. The low level of signal reflected from such a coating will contribute to the improvement of the electromagnetic environment and hygienic standards in the vicinity of radio transmitting facilities.