Indium Tin Oxide Film Characterization at 0.1–20 GHz Using Coaxial Probe Method

Indium tin oxide (ITO) is one of the most commonly used optically transparent conductors in applications, such as electro-optic antennas, displays, and optical coatings. However, their RF frequency-dependent electrical properties have not been reported in the literature. In this paper, we present measurements of the electrical properties (permittivity and conductivity) of ITO films in the 0.1-20-GHz frequency range. Measurements were carried out using an in-house open-ended coaxial probe technique employing a one-port reflection coefficient. As usual, calibration and numerical post-processing is needed to extract the electrical properties of the ITO film placed on a 0.5-mm-thick Eagle glass. The measured conductivity was on the order of 10⁵ throughout the frequency range, and the real and imaginary parts of the permittivity were on the order of 10⁶ at lower frequencies and 10⁵ at higher frequencies.