MICROWAVE-COMPATIBLE, HIGH-TC SUPERCONDUCTING FILMS ON SAPPHIRE SUBSTRATES

AMONG THE POTENTIAL APPLICAITONS OF THE NEW HIGH-TEMPERATURECERAMIC SUPERCONDUCTORS ARE MICROWAVE DEVICES FOR COMMUNICATIONS APPLICATIONS. FABRICATION OF SUCH DEVICES WILL REQUIRE WILL-CONTROLLED TECHNIQUES FOR PREPARING THIN FILMS OF THE MATERIALS ON SUBSTRATES HAVING LOW MICROWAVE LOSSES SUCH AS SINGLE-CRYSTAL ALUMINA (SAPPHIRE). THE INNOVATIVE FEATURE OF THIS PROJECT WILL BE TO FORM HIGH- TEMPERATURE SUPERCONDUCTOR FILMS ON SAPPHIRE WITH A BUFFER LAYER INTERPOSED BETWEEN THE SUBSTRATE AND FILM TO ALLEVIATEINTERFACE PROBLEMS SUSH AS CHEMICAL INTERACTIONS AND THERMALEXPANSION MISMATCH. TO PROMOTE WELL-ORDERED CRYSTAL GROWTH OF THE SUPERCONDUCTOR LAYER, THE BUFFER LAYER MUST BE DEPOSITED EPITAXIALLY ON THE SUBSTRATE, AND CLOSE CRYSTAL- LATTICE MATCHING BETWEEN THE BUFFER MATERIAL AND SUBSTRATE ARE REQUIRED. SEVERAL MATERIALS - INCLUDING ZRO2, LAGAO3 AND LAALO3, - WILL BE INVESTIGATED FOR THEIR SUITABILITY AS BUFFER LAYERS, AND DOUBLE-LAYER BUFFERS WILL ALSO BE CONSIDERED AS A MEANS OF SATISFYING THE DIFFERENT REQUIREMENTS. THE EFFORT EMPHASIZES THE USE OF A SINGLE TECHNIQUE, PULSED LASER DEPOSITION, FOR FORMING BOTH THE BUFFER LAYERS AND SUPERCONDUCTOR FILMS. MICROWAVE DEVICE APPLICATIONS WHICH COULD BENEFIT FROM THE AVAILABILITY OF HIGH-T FILMS ON SAPHIRE SUBSTRATES INCLUDE PASSIVE COMPONENTS SUCH AS RESONATORS, FILTERS, AND STRIPLINES AND ACTIVE DETECTORS AND MIXERS BASED ON JOSEPHSON TUNNELING PHENOMENA.