Doped Josephson Tunnel Barriers
Original Publication Date: 1985-Mar-01
Included in the Prior Art Database: 2005-Feb-18
In Nb Josephson devices, Nb2O5 is used to form tunnel barriers between a Nb base electrode and a counterelectrode. It is difficult to form junctions with pure Nb2O5 . Disordered Nb2O5 has structural degrees of freedom (crystallographic shear) which may contribute to this problem. Crystallographic shear planes can be eliminated by forming compounds having a tungsten bronze symmetry. This is done by forming solid solutions of Nb2O5 with other oxides. In order to eliminate crystallographic shear planes in the tunnel barriers of Nb Josephson devices in a manner which is compatible with processing steps, the tunnel barrier can be formed of a solid solution PbO"xNb2O5 . The crystallographic shear planes result in a distribution of Nb-Nb distances with two main groups: one around 2 ˜ and the other around 4 ˜.