Ramp-type Josephson junctions prepared onsuperconducting MgB2 thin films

摘要

We report demonstration of Josephson effect on ramp-typeMgB2/AlOx/Al/Nb junctions. The MgB2 films were prepared by sequentiale-beam evaporation of boron and magnesium on buffered silicon substrateheld at room temperature, and synthesised by short post-annealing at700oC. The prepared smooth nanocryastalline films with maximal criticaltemperature Tco ≈ 36K were covered by a SrTiO3 overlayer. Ramp-edgewas patterned by ion beam etching through photoresist mask. DCmagnetron sputtering of Al and Nb was applied to complete the junctionstructure. Current-voltage characteristics and current steps at irradiation ofsamples by microwaves confirm the presence of weak link effects in thestructure.