Measurements and Analysis of Microwave Nonlinearities in Ferroelectric Thin Film Transmission Lines

This work evaluates the microwave nonlinear properties of ferroelectric BaSrTiO thin films by measuring the frequency response of several coplanar transmission lines and interdigital capacitor structures as a function of the applied electric field from 150 Hz to 40 GHz. From these measurements, we obtain the distributed nonlinear capacitance C(V_dc) as a function of dc bias. We also measure the harmonic generation at microwave frequencies in ferroelectric transmission lines, and use an accurate circuit model to obtain C(V_rf), the nonlinear capacitance as a function of RF bias. Information about the tuning speed of the film is obtained from a comparison between the two nonlinear capacitances. Characterization of this mechanism is also required to assess the spurious signal generation in ferroelectric-based devices