Fabrication of Nb3Ge/Si(SiOx)/Pb Josephson tunneling junction

The Josephson junction of Nb
3
Ge was fabricated by using a Si(SiO
x
) thin film as the tunnel barrier and Pb as a counter electrode. The thickness of the Si barrier is 2 nm, and the junction size is 0.5 × 0.5 mm
²
. The critical current of the junction was 8 ∼ 12 Acm
^-2
. the normal-state tunneling resistance was
30 \sim 60 \mu \Omega
cm
2
. The onset voltage of gap was 5.2 mV. The Shapiro step mode and the Fiske step mode were observed in a well-defined shape. The dependence of maximum dc-Josephson current upon external magnetic field gives the penetration depth of Nb
3
Ge of 130 nm. The dependence of the resonance voltage upon external magnetic field gives the dielectric constant 8.7 of the Si(SiO
x
) barrier.