Insulator interface effects in sputter-deposited NbN/MgO/NbN (superconductor--insulator--superconductor) tunnel junctions

Journal Article · Wed Jul 01 04:00:00 EDT 1987 · J. Vac. Sci. Technol., A; (United States)

DOI:https://doi.org/10.1116/1.574517· OSTI ID:6448717

Thakoor, S; Leduc, H G; Stern, J A; Thakoor, A P; Khanna, S K

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), Journal Name: J. Vac. Sci. Technol., A; (United States) Journal Issue: 4 Vol. 5:4; ISSN JVTAD
• Country of Publication: United States
• Language: English

Related Subjects

420201* -- Engineering-- Cryogenic Equipment & Devices
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ALKALINE EARTH METAL COMPOUNDS
CHALCOGENIDES
ELECTRICAL PROPERTIES
ELECTRON TUBES
ELECTRONIC EQUIPMENT
EQUIPMENT
ETCHING
FABRICATION
INTERFACES
JUNCTIONS
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
MAGNETRONS
MICROWAVE EQUIPMENT
MICROWAVE TUBES
NIOBIUM COMPOUNDS
NIOBIUM NITRIDES
NITRIDES
NITROGEN COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PNICTIDES
REFRACTORY METAL COMPOUNDS
SPUTTERING
SUPERCONDUCTING JUNCTIONS
SURFACE FINISHING
TRANSITION ELEMENT COMPOUNDS
TUNNEL EFFECT