Ferroelectrics-on-Superconductor Devices: Phased-Array Radar and 10–100 GHz Devices
The first invention using high-T c superconductors on ferroelectric films (or high-dielectric paraelectric materials such as strontium titanate or BST that are nearly ferroelectric) were from the University of Colorado group involving Hermann, Yandrofski, Price, Barnes, and Scott [464, 465, 466]. These devices (Figs. 13.1 and 13.2) incorporated the superconductor merely as a ground plane, with the ferroelectric film in transverse geometry (interdigitalized electrodes, no field across the film thickness) and a micro-stripline configuration (Figs. 13.3 and 13.4) . The fundamental advantage of such devices was in their ability to provide very large phase shifts (> 25%) at very low voltages, and to operate in the 10–20 GHz regime at low loss (Q > 1000, loss tangent < 1%) . Prior to this work, ferroelectrics had traditionally been viewed as unsuitable for microwave devices . Hermann’s group successfully fabricated devices on both YBCO (Yttrium Barium Copper Oxide) and the thallium-based high-T c superconductors. A variety of devices were made and characterized by Galt, Price, and Ono .
KeywordsLoss Tangent Microstrip Antenna Strontium Titanate Ferroelectric Film Damage Surface Layer
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