Nonlinear effects in thin-film ferroelectric transmission lines at microwave frequencies

In order to investigate the switching dynamics of ferroelectric materials at nanosecond time scales, we have measured the nonlinear response of ferroelectric-loaded transmission lines at microwave frequencies. We analyzed the third harmonic and intermodulation products produced by planar transmission lines incorporating ferroelectric thin films, and obtained the rf nonlinear capacitance C(Vrf). We also directly measured the change in capacitance of the same structures due to a dc applied voltage, C(Vdc). By comparing these two experimentally-determined nonlinear capacitances, we are able to directly determine if the mechanisms responsible for the capacitance tuning in these materials are able to responsd on nanosecond time scales.