High Tc S-I-S and S-N-S structures using RF sputtered films

Crosses consisting of 150-μm-wide lines of Y-Ba-Cu-O separated by layers of yttrium-stabilized zirconia about 30-nm thick have been formed using RF diode sputtering and wet chemical patterning. The resistivity of the insulator has been measured as a function of temperature and was found to increase exponentially as the temperature was lowered, reaching values of 10⁹ Ω-cm at 225 K. S-N-S (superconductor/normal metal/superconductor) structures have been fabricated from these crosses by ion-milling a 100-μm-diameter hole through the junction region and depositing Au in the resulting via. After annealing in O₂ at 450°C, the gold supports a supercurrent of up to 1.5 mA at 4.2 K, corresponding to a current density of about 3×10³ A/cm³