Ferroelectric thin film characterization using superconducting microstrip resonators

We describe a novel technique for characterizing the dielectric response of ferroelectric thin films at microwave frequencies. The method involves a microstrip resonator which incorporates a ferroelectric capacitor at its center. To demonstrate this method rye have fabricated a superconducting microstrip resonator from a laser-ablated YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) film on a LaAlO/sub 3/ (LAO) substrate with a SrTiO/sub 3/ (STO) capacitor at its center. We report the observed dielectric behavior of the STO laser ablated film as a function of bias at liquid He and N/sub 2/ temperatures and at high and low frequencies. It is observed that the electrically tunable dielectric constant of the STO film is roughly independent of frequency up to 20 GHz (especially at high bias). The loss tangent of the STO/LAO capacitor decreases with increasing bias and is apparently independent of frequency between 6 and 20 GHz.<>