Laser ablated ferroelectric and superconducting thin films for microwave applications

Electrically tunable microwave components incorporating high temperature superconductors offer both controllability and low conductor losses. Potential applications for such technology are, for example, electrically steerable phase-array antennas, and frequency agile filters. Changes in the resonant frequency of a microwave circuit in response to an applied electric field can be achieved by incorporating ferroelectric materials into the resonant structures. Tunability is achieved since the dielectric constant of the ferroelectric layer can be modified by the electric field. Clearly, an understanding of the behaviour of hybrid superconductor-ferroelectric materials at microwave frequencies is essential in order to realise practical applications. In this paper we present data for the response of a coplanar resonator. Layers of strontium titanate (STO) and YBa₂Cu₃0 ₇ (YBCO) are laser ablated onto an MgO substrate and the resonator is photolithographically etched onto the surface of the YBCO