Excess-current-free stacked Josephson junctions with high <f>IcRn</f> product

We have successfully demonstrated the elimination of excess currents in interface-treated Josephson junctions (ITJs) having vertically stacked trilayer structure based on c-axis oriented YBa<f>2</f>Cu<f>3</f>O<f>7−δ</f> (YBCO) films. Several experimental results obtained so far suggest that the excess currents are transported via superconducting short paths formed in the tunnel barrier. Considering that short paths are made of YBCO, we intend to patch the paths into insulators by doping PrGaO<f>3</f>, after the amorphous layer on the surface of the base YBCO electrode was formed by etching process. The other fabrication sequences are the same as the previous ones. The obtained ITJs showed excellent resistively shunted-junction type current–voltage (I–V) characteristics and almost 100% of modulation depth of the critical current for an external magnetic field at 4.2 K. Even for smaller value of <f>Jc</f>, the vertically stacked type ITJs showed almost the same <f>IcRn</f> value as that obtained for ramp-edge type IMJs with higher <f>Jc</f>. Furthermore, the yield is remarkably improved by using this technique. [Copyright &y& Elsevier]