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Nb3Al/oxide/Pb Josephson tunnel junctions have been fabricated using a new surface cleaning technique, the CF4 cleaning process (CFCP), in which the base electrode is cleaned prior to oxide barrier formation in an Ar and CF4, rf plasma mixture. Adopting lower cleaning voltages than for Nb/oxide/Pb junctions, makes it possible to obtain high-quality junctions with very low leakage (Vm=30 mV) and uniform Josephson current distribution. Such good junction characteristics indicate the formation of damage-free cleaned electrode surfaces and highly insulating mixed oxide barriers.
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Tanabe et al. (1983) studied this question.
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