Small Nb/Al-Oxide/Nb Josephson Junction Fabrication Using Lift-Off Processes

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Abstract
A lift-off technique is applied to the fabrication of all-refractory Nb/Al-oxide/Nb Josephson tunneling junctions. It is found that the lift-off is very efficient for lowering the influence of stresses in refractory metal electrode on junction characteristics. Small junctions (1 µm) with low leakage current can be fabricated by lift-off technique, whereas an etching process increases leakage currents of small junctions. Current-voltage characteristics of Vm=25 mV at a current density of 10 kA/cm2 and a junction current standard deviation of 3.2% in 1 µm size junctions are obtained.