Effect of Ag layer thickness and annealing treatment on the transmittance and conductivity of transparent antennas fabricated using ITO/Ag/ITO structures

Wireless communication is the mainstay of the modern information infrastructure, creating a growing demand for innovative antenna technologies. Transparent antennas combine high optical transparency and effective radio frequency performance to address the limitations of conventional opaque metal antennas. They have also expanded their application possibilities to smartphones, wearable devices, automotive windows, and building surfaces. In this study, we investigated a dielectric–metal–dielectric (DMD) structured transparent conductive film, using an indium tin oxide (ITO)/Ag/ITO three-layer structure to balance high transmittance and conductivity. The films were deposited using a DC-facing target sputtering system with varied Ag layer thicknesses and subsequently heated (annealed) at temperatures ranging from 200 to 500 °C. The optical transmittance, sheet resistance, and carrier density were measured, and a fabricated monopole antenna (20 × 5 mm2) was used to evaluate the radiation efficiency. An Ag layer with a thickness of 7.5 nm exhibited a 73.3% transmittance at 650 nm and a conductivity of 7.8 × 105 S/m in the as-deposited state. After annealing at 300 °C, the transmittance increased to 76.0% and 8.3 × 105 S/m. These results highlight the potential of ITO/Ag/ITO DMD films for advancing the transparent antenna technology for next-generation wireless communication systems.