HIGH-T-C EDGE-GEOMETRY SNS WEAK LINKS ON SILICON-ON-SAPPHIRE SUBSTRATES

High-quality superconductor/normal-metal/superconductor (SNS) edge-geo metry weak links have been produced on silicon-on-sapphire (SOS) subst rates using a new SrTiO3/''seed-layer''/cubic-zirconia (YSZ) buffer sy stem. The seed layer is a thin YBa2Cu3O7-x (YBCO) or PrBa2Cu3O7-x (PBC O) film, which provides a template for growth of the SrTiO3. This mult ilayer buffer system eliminates problems with series grain-boundary we ak links seen in edge junctions on single YSZ buffer layers on SOS, wh ile the use of moderate-dielectric-constant SOS substrates should bene fit high-frequency applications and enable integration with silicon ci rcuitry. SNS weak links fabricated on SOS with PBCO and Co doped YBCO normal-metal layers exhibit current-voltage characteristics qualitativ ely consistent with the resistively shunted junction model, with modul ating AC Josephson steps and operation to temperatures above 77 K. The se are the first reported epitaxial edge-geometry SNS devices on SOS s ubstrates.