HIGH T-C STEP-EDGE JOSEPHSON-JUNCTIONS ON SILICON SUBSTRATES

The epitaxial buffer system CeO2/YSZ was used to prepare YBCO films of high crystalline quality on silicon substrates by laser deposition. An advanced technique of step preparation in the YSZ buffer layer preserved the critical current densities of j(C) (77 K)similar to 10(6) A/cm(2) for 30 nm thick YBCO films also in the etched parts of the substrate. Further, a homogeneous growth over the 35 to 45 nm deep steps was observed. So we were able to realize step-edge Josephson junctions with critical temperatures up to 77 K. Our dc SQUIDs on silicon substrates showed voltage modulation 74 K. (C) 1995 American Institute of Physics.