High critical temperature SNS Josephson microbridges
This thesis work presents a new technique for reproducibly fabricating superconductor-normal metal-superconductor (SNS) Josephson microbridges which can be used with a wide variety of superconductors and normal metals. This technique has been used to make the first high-T/sub c/ SNS microbridges and dc SQUIDS's, employing Nb/sub 3/Ge or Nb/sub 3/Sn for the superconductor and Cu for the normal metal. These devices have the widest operating temperature range of any Josephson device, among other advantages. They have nearly ideal characteristics: sharply defined critical currents (l/sub c/) with a voltage rise resembling a square root behavior, large l/sub c/R/sub n/ products, and heating restricted to large dissipation. The modulation of the critical current in an applied magnetic field is nearly ideal and sharp constant voltage steps are observed in the current-voltage characteristic when microwaves are applied. These properties are compared with the Likharev-Usadel model for the I/sub c/R/sub n/ product, modified to take into account out geometry. Reasonable agreement is found with the predictions of the model, both as a function of temperature and as a function of bridge length. The latter has been made possible for the first time due to the reproducibility of our technique. New boundary conditions are presented for this model. The dynamic behavior is described by the time-dependence Ginzburg-Landau theory. Calculations for the current-voltage characteristics and new results are shown which include the effect of microwaves. Both of these are in excellent agreement with the measured characteristics. Further possibilities for using this fabrication procedure in studies of basic physics and useful applications are investigated.
- Research Organization:
- Stanford Univ., CA (USA)
- OSTI ID:
- 6202186
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALLOY SYSTEMS
ALLOYS
BINARY ALLOY SYSTEMS
BOUNDARY CONDITIONS
COPPER
CRITICAL CURRENT
CRITICAL TEMPERATURE
CURRENTS
ELECTRIC CURRENTS
ELECTRONIC EQUIPMENT
ELEMENTS
EQUIPMENT
FABRICATION
FLUXMETERS
GERMANIUM ALLOYS
GINZBURG-LANDAU THEORY
JOSEPHSON JUNCTIONS
JUNCTIONS
MATHEMATICAL MODELS
MEASURING INSTRUMENTS
METALS
MICROWAVE EQUIPMENT
NIOBIUM ALLOYS
NIOBIUM BASE ALLOYS
PHYSICAL PROPERTIES
SQUID DEVICES
SUPERCONDUCTING DEVICES
SUPERCONDUCTING JUNCTIONS
TEMPERATURE DEPENDENCE
THERMODYNAMIC PROPERTIES
TIN ALLOYS
TRANSITION ELEMENTS
TRANSITION TEMPERATURE