YBACUO-BASED SUPERCONDUCTOR-INSULATOR-SUPERCONDUCTOR DETECTOR FOR LONG-WAVELENGTH INFRARED APPLICATIONS

SUPERCONDUCTOR-INSULATOR-SUPERCONDUCTOR (SIS) JUNCTIONS OF HIGH TC, YBACUO-TYPE MATERIALS FOR LONG WAVELENGTH INFRARED (LWIR) DETECTION ARE BEING INVESTIGATED. THE FEASIBILITY IS BEING DETERMINED OF USING GALLIUM-ARSENIDE AS THE SUBSTRATE MATERIAL FOR THE HIGH TC SUPERCONDUCTING MATERIALS OF THE YBACUO TYPE. A DETERMINATION IS BEING MADE IF PROCESSING STEPS SUCH AS PHOTOLITHOGRAPHY, CONTACT METALLIZATION ORCHEMICAL ETCHING ADVERSELY EFFECT THE SUPERCONDUCTING PROPERTIES OF SINGLE LAYERS. THE FABRICATION OF THE SIS STRUCTURE AND THE MEASUREMENT OF ITS SUPERCONDUCTIVE TRANSITION IS BEING UNDERTAKEN TO DETERMINE IF SPUTTERING AN INSULATOR ON THE HIGH TC SUPERCONDUCTORS POISONSTHE SURFACE RENDERING THEM UNUSABLE FOR SENSOR FABRICATION. YABACUO SIS JUNCTIONS ARE BEING RADIO FREQUENCY-SPUTTERED AND THEN ANNEALED INSITU IN AN OXYGEN ATMOSPHERE. WHEN SUCCESSFUL, THESE JUNCTIONS ARE EXPECTED TO YIELD SUPERCONDUCTORS WITH TRANSITION TEMPERATURES LARGER THAN 77K. THE CURRENT VOLTAGE CHARACTERISTICS OF SUCH A JUNCTION ARE BEING MODULATED BY INCIDENT LWIR RADIATION. THE SIS JUNCTION WOULD, THEREFORE, FUNCTION AS A VOLTAGE CONTROLLED SENSOR. LWIR SENSING IS THE BASIS OF SEVERAL DEFENSE AND COMMERCIAL APPLICATIONS, INCLUDING DETECTION AND TRACKING OF INCOMING MISSILE AND INFRARED SPECTORSCOPY FOR WEATHER FORECASTING.