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Öğe A comprehensive review of recent methods for compactness and performance enhancement in 5G and 6G wearable antennas(Elsevier B.V., 2024) Saleh, S.; Saeidi, T.; Timmons, N.; Razzaz, F.Wearable antennas are important in many areas of our lives, including the Internet of Things (IoT), health care, sports, the automobile industry, security, and entertainment. Wearable antennas should be designed with a compact size in order to be readily integrated and conform to the body shape, as well as a high performance to withstand mechanical and environmental changes. 5 G and 6 G technologies offer sufficient solutions for wearable antennas utilized for wireless body area networks (WBANs) and IoT applications in terms of high reliability, high gain, compactness, low cost, and high performance. In this work, we present for the first time a comprehnsive review of 5 G and 6 G wearable antennas discussing their significance, types, applications, and design issues in detail. A state-of-the-art for the recent 5 G wearable antenna reviews is also outlined. The main contribution of this work is explaining the compactness and performance enhancement methods at both bands in ascending order starting from low frequency, sub 6 GHz, 5 G mmWave, up to 6 G (high mmWavw and THz wave), so the reader will differentiate between the antennas’ design requirements and challenges for different bands easily. The impacts of flexibility, bending, and on-body/off-body on antenna performance as well as specific absorption rate (SAR) calculation are also taken into account. This review can be considered a valuable tool for designers and researchers in designing many types of wearable antennas at 5 G and 6 G frequency bands for various applications by understanding the antenna's design problems, topologies, and types of substrate and conductive materials. © 2024 The AuthorsÖğe Enhanced performance of Pb/FeSe2 interfaces designed for electrical applications(Springer, 2024) Alharbi, Seham R.; Qasrawi, Atef Fayez; Algarni, Sabah E.In this work, iron selenide layers are deposited onto glass and lead substrates to perform as terahertz filters. The layers are deposited by the thermal evaporation technique under a vacuum pressure of 10–5 mbar. Glass/FeSe2 (GFS) and Pb/FeSe2 (PFS) films are structurally, morphologically and electrically characterized. The atomic composition of the GFS films contained excess selenium that reacted with Pb forming a PbSe layer. This layer induced the crystallinity of iron selenide. The preferred crystal structure of FeSe2 was cubic with cell parameters of a = b = c = 3.04 Å and space group Pm3m . Lead substrates increased the room temperature electrical conductivity of GFS films from of 1.52 ×10?5(?cm)?1 to 6.88 ×10?2(?cm)?1 . Analyses of the electrical conduction mechanism in the temperature range of 25–330 K have shown that coating the films onto Pb substrates shifted the accepter level from 182 to 58 meV, decreased the degree of structural disor-der, shorten the average hopping range from 59 to 19 Å and increased the density of localized states near Fermi level by two orders of magnitude. The conductivity of PFS films exhibited degenerate semiconductor characteristics in the temperature range of 120–28 K. This feature is followed by an evidence of exhibiting superconductivity at critical temperatures lower than 24 K. On the other hand the impedance spectroscopy measurements in the driving signal frequency domain of 0.01–1.0 GHz have shown that Pb/FeSe2/Ag interfaces can perform as band filters showing microwave cutoff frequency values reach-ing 100 GHz at driving signal frequency of 1.0 GHz. These band filters are ideal for 6G technology nominating PFS films for high frequency applications.
