Electromagnetic characterization of transparent conducting thin films using two‐port flange coaxial probe and thin‐film transfer matrix method

Abstract

An efficient method to determine the electromagnetic characteristics of transparent conducting oxide (TCO) thin films is presented herein. When a two-port flange coaxial probe is used for electromagnetic characterization, it is important to note that since the thickness of the film is very thin, it should be taken into account that the measured S parameters not only correspond to the thin film, but also to the substrate. The main idea of this study is to exploit the S parameters corresponding solely to the thin film by employing transfer matrix method. Then, by using the obtained S parameters, the effective conductivity (σ) and relative permittivity (ε r) of the TCO thin film are determined. By applying this method to a sample under test, the conductivity and relative permittivity are obtained in the order of 10 5 (S/m) and 10 6 in the 2-20 GHz frequency range, respectively. These results are compared with those obtained by the Nicolson-Ross-Wier and open-ended coaxial probe methods. Simulation results show that when the TCO thin film thickness reaches 0.5 mm, its conductivity increases up to two times. Also, when the gap between the coaxial probe and the thin-film surface is 0.1 mm, the conductivity approaches zero. Using this method, the material and thickness of the substrate have slight effect on determining the electromagnetic characteristics. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.