Ar ion bombardment effects of NbN/Pb Josephson junctions with plasma oxidized barriers

Journal Article · Thu Dec 01 04:00:00 EST 1983 · J. Appl. Phys.; (United States)

DOI:https://doi.org/10.1063/1.331973· OSTI ID:7050050

Hikita, M; Takei, K; Igarashi, M

Details of the relation between Ar ion bombardment effects on NbN surface and I-V characteristics of NbN/Pb junctions with plasma oxidized barriers have been studied. NbN base electrodes, which behave as a strong coupling superconductor (T/sub c/>15 K, 2..delta../kT/sub c/ = 4.2--4.3), were prepared onto substrates at 300 /sup 0/C by reactive dc magnetron sputtering. In the NbN/Pb junction fabrication, cathode self-bias voltage V/sub CSB/ during Ar sputter cleaning strongly influences the subgap leakage current value, which increases with V/sub CSB/. The V/sub CSB/ also influences normalized normal tunnel resistance AR/sub NN/. It is found, in reflection electron diffraction and x-ray photoelectron spectroscopy studies, that the Ar ion bombardment at V/sub CSB/> 200 V on a NbN surface produces an amorphous structure in the surface layer. It is also found that the thickness of amorphous layer increases with Ar ion energy. Based on the experimental results, low subgap leakage current junctions, where V/sub m/ exceeds 100 mV at 4.2 K, were fabricated under low energy plasma oxidation conditions, where V/sub m/ is the product of Josephson critical current and subgap resistance. Sputter cleaning and plasma oxidation conditions for obtaining high quality junctions are also discussed.

• Research Organization: Ibaraki Electrical Communication Laboratory, Nippon Telegraph and Telephone Public Corporation, Tokai, Ibaraki 319-11, Japan
• OSTI ID: 7050050
• Journal Information: J. Appl. Phys.; (United States), Journal Name: J. Appl. Phys.; (United States) Vol. 54:12; ISSN JAPIA
• Country of Publication: United States
• Language: English

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71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
AMORPHOUS STATE
ARGON IONS
CHARGED PARTICLES
CHEMICAL REACTIONS
CLEANING
COLLISIONS
CURRENTS
DIMENSIONS
ELECTRIC CONDUCTIVITY
ELECTRIC CURRENTS
ELECTRIC POTENTIAL
ELECTRICAL PROPERTIES
ELEMENTS
FABRICATION
ION COLLISIONS
IONS
JOSEPHSON JUNCTIONS
JUNCTIONS
LEAD
LEAKAGE CURRENT
METALS
NIOBIUM COMPOUNDS
NIOBIUM NITRIDES
NITRIDES
NITROGEN COMPOUNDS
OXIDATION
PHYSICAL PROPERTIES
PHYSICAL RADIATION EFFECTS
PLASMA
PNICTIDES
RADIATION EFFECTS
SUPERCONDUCTING JUNCTIONS
SURFACE CLEANING
SURFACE FINISHING
THICKNESS
TRANSITION ELEMENT COMPOUNDS