Fabrication and dc characteristics of small-area tantalum and niobium superconducting tunnel junctions

Journal Article · Thu Oct 15 00:00:00 EDT 1987 · J. Appl. Phys.; (United States)

DOI:https://doi.org/10.1063/1.339332· OSTI ID:6223783

Face, D W; Prober, D E

We discuss the fabrication and dc electrical characteristics of small-area (1--6 ..mu..m/sup 2/) superconducting tunnel junctions with Ta or Nb base electrodes and Pb or Pb/sub 0.9/Bi/sub 0.1/ counterelectrodes. These junctions have very small subgap leakage currents, a ''sharp'' current rise at the sum-gap voltage, and show strong quantum effects when used as microwave mixers. The use of a low-energy (--150 eV) ion cleaning process and a novel step-defined fabrication process that eliminates photoresist processing after base electrode deposition are discussed. Tunnel barriers formed by dc glow discharge oxidation were the most successful. Tunnel barrier formation by thermal oxidation and ion-beam oxidation is also discussed. An oxidized Ta overlayer (--7 nm thick) was found to improve the characteristics of Nb-based junctions. The electrical characteristics of junctions with different electrode and barrier materials are presented and discussed in terms of the physical mechanisms that lead to excess subgap current and to a width of the current rise at the sum-gap voltage.

• Research Organization: Section of Applied Physics, Yale University, P. O. Box 2157, New Haven, Connecticut 06520
• OSTI ID: 6223783
• Journal Information: J. Appl. Phys.; (United States), Journal Name: J. Appl. Phys.; (United States) Vol. 62:8; ISSN JAPIA
• Country of Publication: United States
• Language: English

Related Subjects

420201* -- Engineering-- Cryogenic Equipment & Devices
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALLOYS
BISMUTH ALLOYS
CHEMICAL REACTIONS
DATA
ELECTRIC DISCHARGES
ELECTRICAL PROPERTIES
ELECTRODES
ELEMENTS
EXPERIMENTAL DATA
FABRICATION
GLOW DISCHARGES
INFORMATION
JUNCTIONS
LEAD
LEAD ALLOYS
METALS
NIOBIUM
NUMERICAL DATA
OXIDATION
PHYSICAL PROPERTIES
SUPERCONDUCTING JUNCTIONS
TANTALUM
TRANSITION ELEMENTS
TUNNEL EFFECT