Thin Film Technology of High-Critical-Temperature Superconducting Electronics

摘要

The objective of this three-year program was to develop a technology of Josephson tunnel junctions capable of operating at temperatures above 10K. The superconducting electrode materials investigation were V3Si, Nb3Sn and Mo-Re. Tunnel barriers were formed mostly by oxidizing metallic overlayers of Al and Y. Superconductor/barrier interfaces were characterized by surface-analytical techniques. The results of characterization permitted fabricated of junctions with Nb3Sn and Mo-Re base electrodes and Pb, Pb-Bi and Mo-Re counterelectrodes having nearly ideal current-voltage characteristics. These counterelectrodes were deposited at temperatures not exceeding T = 100 C. The Mo-Re counterelectrode formed at low T had a critical temperature, Tc, of only 8K. A high-critical-temperature Nb3Sn counterelectrode requiring high deposition temperatures could not be fabricated successfully. The main cause of this negative result was the nonuniform coverage of the base with overlays which contained thin or defective spots. In contrast to Nb3Sn high-Tc NbN counterelectrodes were successfully fabricated and sumgap voltages exceeding 5 mV were measured at 4.2K. The report contains new information on artificial barriers and on Mo-Re and Nb3Sn superconducting films. (Author)