Effect of annealing treatment of indium tin oxide thin films on film properties and transparent antenna properties

There is a growing demand for transparent thin film antennas to serve as access points for wireless communication that can be installed at any location without compromising visibility, while retaining the versatility of existing antennas. Although studies exist on indium tin oxide (ITO)-based transparent antennas, studies on the effect of thin-film process parameters on antenna properties are rare. In this study, we deposited ITO, which resonates at 3.3 GHz, using the facing target sputtering method with different thicknesses ranging from 400 to 2000 nm, from a typical thin film to a relatively thick film. ITO thin films deposited at room temperature were annealed in air at 200, 300, and 400 °C in an electric furnace. The optically transparent monopole antennas were fabricated using air-annealed ITO films. The effects of the annealing temperature on the film and antenna properties were investigated. A high radiation efficiency of 70.8 % was achieved while maintaining a transmittance of more than 70 % for a 2000 nm ITO film annealed at 400 °C. The results indicate that tailoring appropriate conductive film properties for desired transmittance is crucial to realize the expected antenna performance.