Fabrication of high quality Nb/AlO/sub x/-Al/Nb Josephson junctions. I. Sputtered Nb films for junction electrodes

The stress, surface morphology, superconducting characteristics, and crystal structure of sputtered Nb films were evaluated to judge their applicability to Josephson-junction electrodes. The film qualities were compared between Nb films deposited by DC and RF magnetron sputtering. The authors concluded that DC-sputtered Nb films are more suitable for junction electrodes and studied the relationship between their film quality and sputtering parameters. They observed that the Nb film characteristics were determined solely by the cathode voltage during sputtering regardless of the other parameters. The authors discuss the changes in film characteristics during Josephson integrated circuit processing.<
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