Electrochromic Thin Films WO3-LiNbO3-NiO Broadband Microwave Characterization at Various Temperatures

This paper describes, for the first time, dielectric characterization of an electronically tunable electrochromic (EC) thin film material using a temperature- controlled microstrip line method between 7C to 50C in a broad frequency band of 1-67 GHz. The two ends of the microstrip line, directly exposed to the tunable EC material, are connected to two broadband CPW to microstrip line transitions. The transitions allow the application of a dc bias voltage for electric stimulation of the material and facilitate on-wafer RF measurements using a standard CPW probe station. In addition, SiO2 is used as a known material to evaluate dielectric extraction algorithm and to establish an understanding of wave propagation mechanism in thin film microstrip lines (TFMLs). This information can help the designer to properly exploit the potentials of the newly introduced tunable material. Finally, the experimental results suggest a broader operating temperature range for this first generation of tunable EC material compared to some liquid crystals such as K15