Broadband Microwave Characterization of Nanostructured Thin Film With Giant Dielectric Response

This paper describes the extraction of the dielectric properties of a nanostructured thin film from two-port S-parameter measurements on coplanar waveguide (CPW) lines. The CPW line is on top of a bilayer structure formed by a supporting glass substrate and a dielectric thin film made by dispersing silver nanoparticles inside a polymer host. A dispersion mechanism due to internal inductance of the CPW line when calculating the effective dielectric constant is investigated. The extraction involves conformal-mapping approximation that uses closed-form equations to calculate the dielectric constant and the loss tangent of each layer based on the effective dielectric constant and loss tangent of the entire structure. Additionally, computer-aided-design model with a direct fitting technique are deployed for further investigation of potential multimode propagation for a CPW line with a substrate that has a very large dielectric constant. The results of the two techniques are compared and discussed. The measured dielectric constant ranges from 3×10⁴ to 4.6×10³ from 1 to 20 GHz with a loss tangent of 0.55 to 1.75 from 1 to 20 GHz.