Characterization of a tunable thin film microwave YBa2Cu3O7−x/SrTiO3 coplanar capacitor

Abstract

We have fabricated and characterized electrically tunable high temperature superconductor coplanar microstrip resonators incorporating tunable SrTiO₃ ferroelectric thin films. The low frequency capacitance of the SrTiO₃ capacitor is measured directly. High frequency capacitance and loss information are extracted from the observed resonances and compared with the low frequency data. Hysteresis loops display an onset of ferroelectricity at 160 K. The spontaneous charge and coercive voltage (at 10 kHz) as a function of temperature are extracted from these loops.