Complete stabilization and improvement of the characteristics of tunnel junctions by thermal annealing

The authors have observed that submicron sized Al–AlOx–Al tunnel junctions can be stabilized completely by annealing them in vacuum at temperatures between 350 and 450°C. In addition, low temperature characterization of the samples after the annealing treatment showed a marked improvement of the tunneling characteristics due to the disappearance of unwanted resonances in the current. Charging energy, tunneling resistance, barrier thickness, and height all increase after the treatment. The superconducting gap is not affected, but supercurrent is reduced in accordance with the increase of tunneling resistance.