Character and fabrication of Al/Al2O3/Al tunnel junctions for qubit application

The superconductive Josephson junction is the key device for superconducting quantum computation. We have fabricated Al/Al₂O₃/Al tunnel junctions using a double angle evaporation method based on a suspended shadow mask. The Al₂O₃ junction barrier has been formed by introducing pure oxygen into the chamber during the fabrication process. We have adjusted exposure conditions by changing either the oxygen pressure or the oxidizing time during the formation of tunnel barriers to control the critical current density J _c and the junction specific resistance R _c . Measurements of the leakage in Al/Al₂O₃/Al tunnel junctions show that the devices are suitable for qubit applications.