YBA2CU3O7-X JOSEPHSON-JUNCTIONS ON BICRYSTAL AL2O3 AND SRTIO3 SUBSTRATES

Bicrystal grain-boundary junctions (bi-GBJs) have been reproducibly fa bricated on SrTiO3 (STO) and r-plane Al2O3 (sapphire) bicrystal substr ates. Sapphire bicrystals are candidates for high-frequency applicatio ns due to their low dielectric constant and loss tangent. The sapphire bi-GBJs demonstrated resistively shunted junction (RSJ)-like current voltage characteristics, with junction parameters comparable to the ST O bi-GBJs and critical current densities J(c) similar to 10(5) A/cm(2) . Independent control of junction resistance (R-N) was demonstrated wi th the used of Au shunt layers. In addition, overlayers such as Au or STO may act to passivate the GBJs and improve long term stability.