On the Role of Surface Oxide Impurities in the 'Knee' Effect in Superconducting Tunnel Junctions.
MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF METALLURGY AND MATERIALS SCIENCE
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The authors present a qualitative model based on the effect of impurity states in the barrier to explain the anomalous knee in the I-V characteristics of superconducting tunnel junctions, they have experimentally confirmed the temperature dependence predicted by the model, and have been able to reproducibly control the appearance, disappearance and the severity of the anomaly by controlled junction fabrication. The junctions were made by evaporating thin films on to the oxidized surfaces of Nb single crystals which had been grown in ultra-high vacua by the floating zone technique. The authors report that control of impurities in the barrier itself rather than surface effects at the metal-oxide interface according to the model can completely control the appearance of the anomaly. Author
- Solid State Physics