Properties of oxide films formed by rfhyphen;plasma oxidation of In/Pb/Au alloys were ellipsometrically investigated. Two types of changes in oxide properties were found during annealing or longhyphen;term roomhyphen;temperature storage for lowhyphen;indiumhyphen;concentration alloys. One is related to excess oxygen associated with plasma oxidation, and the other is attributed to the conversion of oxide composition from a PbOhyphen;In2O3mixture into pure In2O3. For highhyphen;indiumhyphen;concentration alloys, on the other hand, the oxide was revealed to be very stable because it was almost composed of pure In2O3. From these considerations it was concluded that the more stable Pbhyphen;alloy Josephson junctions were expected with the higherhyphen;indiumhyphen;concentration base film, such as more than 30hyphen;wt.thinsp;percnt; alloys.
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