ELECTRON-BEAM LITHOGRAPHY AND ION-IMPLANTATION TECHNIQUES FOR FABRICATION OF HIGH-T-C JOSEPHSON-JUNCTIONS

Established semiconductor process technologies are demonstrated to be suitable for the fabrication of high temperature superconductor (HTS) Josephson junctions. Single YBCO bridges were modified by local oxygen ion irradiation through a narrow slit in a PMMA mask which was formed by electron beam lithography. The influence of slit dimension and irr adiation dose was investigated. The critical current and normal resist ance of the modified microbridges can be controled by these two parame ters. Proximity coupling across the modified region is observed up to a slit width of 250 nm. When exposed to microwave irradiation the micr obridges exhibited Shapiro steps. In dc SQUIDs a voltage modulation as a function of an applied magnetic flux is observed.