Insulator interface effects in sputter-deposited NbN/MgO/NbN (superconductor--insulator--superconductor) tunnel junctions
All refractory, NbN/MgO/NbN (superconductor--insulator--superconductor) tunnel junctions have been fabricated by in situ sputter deposition. The influence of MgO thickness (0.8--6.0 nm) deposited under different sputtering ambients at various deposition rates on current--voltage (I--V) characteristics of small-area (30 x 30 ..mu..m) tunnel junctions is studied. The NbN/MgO/NbN trilayer is deposited in situ by dc reactive magnetron (NbN), and rf magnetron (MgO) sputtering, followed by thermal evaporation of a protective Au cap. Subsequent photolithography, reactive ion etching, planarization, and top contact (Pb/Ag) deposition completes the junction structure. Normal resistance of the junctions with MgO deposited in Ar or Ar and N/sub 2/ mixture shows good exponential dependence on the MgO thickness indicating formation of a pin-hole-free uniform barrier layer. Further, a postdeposition in situ oxygen plasma treatment of the MgO layer increases the junction resistance sharply, and reduces the subgap leakage. A possible enrichment of the MgO layer stoichiometry by the oxygen plasma treatment is suggested. A sumgap as high as 5.7 mV is observed for such a junction.
- Research Organization:
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109
- OSTI ID:
- 6448717
- Journal Information:
- J. Vac. Sci. Technol., A; (United States), Vol. 5:4, Issue 4
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
MAGNESIUM OXIDES
SUPERCONDUCTING JUNCTIONS
NIOBIUM NITRIDES
ELECTRICAL PROPERTIES
FABRICATION
TUNNEL EFFECT
ETCHING
INTERFACES
MAGNETRONS
SPUTTERING
ALKALINE EARTH METAL COMPOUNDS
CHALCOGENIDES
ELECTRON TUBES
ELECTRONIC EQUIPMENT
EQUIPMENT
JUNCTIONS
MAGNESIUM COMPOUNDS
MICROWAVE EQUIPMENT
MICROWAVE TUBES
NIOBIUM COMPOUNDS
NITRIDES
NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PNICTIDES
REFRACTORY METAL COMPOUNDS
SURFACE FINISHING
TRANSITION ELEMENT COMPOUNDS
420201* - Engineering- Cryogenic Equipment & Devices