A transparent antenna array based on silver sandwiched indium tin oxide (AgITO) heterostructure thin films is presented. The AgITO is sputtered on both sides of soda-lime glass (SLG) substrate, and the three thin films deposition parameters are optimized to obtain very low ohmic interfacial contact resistance of less than 1 Ω/Sq. AgITO promotes thin film-based transparent microstrip structure of the proposed antenna array as well as the transparent T-junction power divider. Furthermore, AgITO microstrip as well as opaque single element antenna as reference antennas for a transparent array are presented. The proposed array has wide bandwidth promoting radio frequency energy harvesting at Wi-Fi 2.4, LTE 2600, WLAN, WiMAX and the expected 5G mid-bands. Moreover, it could be functionalized for wireless transmission within the previously mentioned bands. The transparent AgITO array has 5 dBi gain value against 2.3 dBi for the transparent AgITO single element antenna at 5.8 GHz. The array was utilized for radiofrequency energy harvesting, obtaining DC output volt=161.4 mV with a conversion efficiency of 32.9% at 5.8 GHz with RF received power of -10 dBm.
Graphene has been successfully grown on commercial copper foil at low temperature of 500 °C by pulsed laser deposition (PLD). X-ray diffraction patterns showed that films have been grown in the presence of Cu(111) and Cu(200) facets. Raman spectroscopy was utilized to study the effects of temperature, surface structure, and cooling rate on the graphene growth. Raman spectra indicate that the synthesis of graphene layers rely on the surface quality of the Cu substrate together with the proper cooling profile coupled with graphene growth temperature. PLD-grown graphene film on Cu has been verified by transmission electron microscopy. Surface mediated growth of graphene on Cu foil substrate revealed to have a favorable catalytic effect. High growth rate of graphene and less defects can be derived using fast cooling rate.
Graphene oxide/polyvinyl alcohol (GO/PVA) composites have been developed using facile colloidal processing technique to form a super dielectric spacer of 10 6 order. The dielectric characteristics of GO/PVA composite were investigated at a frequency range from 20 Hz to 1 M Hz. The electrical analysis showed a complex interaction that vary from Debye and could be explained using Bruggeman and Maxwell-Garnett assumptions in the high-frequency range and Percolation theory in the low range. Due to the ageing effect and the observed high imaginary part, an investigation of GO film dielectric properties were investigated. The results incorporate a crucial role of water contents on corresponding GO and GO/PVA electromagnetic interaction besides the well-established functional group's theory. Transmission electron microscopy, X-ray diffraction, dispersive Raman, potentiostat/galvanostat and LCR meter were utilized to perform microscopic, structure and electrical characterizations.
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