Some properties of Nb-Nb2O5-Pb(In) Josephson tunnel junctions for devices applications

A detailed investigation of tunneling has been carried out on Nb-Nb
2
O
5
-Pb(In) junctions where the tunnel barrier is made-of Nb
2
O
5
thermal oxide with accurately controlled oxidation parameters. The oxide barrier appears as a n-type semiconductor with two Schottky barriers at the interfaces. The transport of charged oxygen vacancies is supposed to play a fundamental role in the oxidation process. The barrier potential φ and the tunnel resistance R have been related to the oxidation parameters. The junctions realized have sizes ranging from 4 to 10
⁴
μm
²
, the Josephson current density, dependent on the oxide thickness, is in the 1-10
⁵
A/cm
²
range. Very low transition times from the superconductive to the normal state have been observed.