Title :
Ultra-high quality Nb/AlOx/Nb tunnel junctions with epitaxial base layers
Author :
Kirk, E.C.G. ; Blamire, M.G. ; Somekh, R.E. ; Evetts, J.E. ; VanVechten, D. ; Lovellette, M.N.
Author_Institution :
Dept. of Mater. Sci. & Metall., Cambridge Univ., UK
fDate :
3/1/1991 12:00:00 AM
Abstract :
Using an ultra-high-vacuum DC sputtering system, Nb/AlOx/Nb tunnel junction devices with epitaxial Nb base layers have been fabricated. Improvements in device quality that can be achieved by heating the substrates during the growth of the tunnel barrier are investigated. By measuring the subgap characteristic under magnetic field at temperatures down to 0.4 K, it is shown that for V <ΔNb the currents in devices with critical current densities in the range of 105-106 AM-2 follow closely the BCS prediction and show no extrinsic leakage current. The divergence of the curve for higher current densities and at higher voltages is discussed
Keywords :
aluminium compounds; niobium; superconducting epitaxial layers; superconducting junction devices; 0.4 K; BCS prediction; critical current densities; epitaxial Nb base layers; epitaxial base layers; extrinsic leakage current; magnetic field; subgap characteristic; temperatures; ultra-high-vacuum DC sputtering system; Critical current density; Current measurement; Density measurement; Heating; Leakage current; Magnetic field measurement; Niobium; Sputtering; Substrates; Temperature distribution;
Journal_Title :
Magnetics, IEEE Transactions on
