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

Journal Article · Thu Dec 01 00:00:00 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), Vol. 54:12
• Country of Publication: United States
• Language: English

Related Subjects

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