COMPARATIVE-STUDY OF SHUNTED BICRYSTAL JOSEPHSON-JUNCTIONS

In order to optimize the series array performance of YBa2Cu3O7-x (YBCO ) grain boundary shunted junctions, a method to determine and control the junction resistance R(s) and Au/YBCO contact resistivity rho(c) ha s been developed. 200 nm thick c-oriented YBCO films were grown by int ermittent thermal coevaporation opt bicrystal yttria-stabilized zircon ia substrates. A gold contact overlayer of thickness d(n) was deposite d in situ. Normal junction resistances have been measured as a functio n of d(n) and shunt width w. It was shown that, in accordance with the oretical estimates, the junction shunt resistance is essentially contr olled by the c-axis Au/YBCO interface specific resistance and scales a s R(s) = 1/w root rho(c) rho(n)/d(n). The product rho(c) rho(n) simila r or equal to 3 . 10(-14) Omega(2)cm(3) was estimated from the experim ental data, leading to rho(c) approximate to 10(-8) Omega cm(2) for ty pical values of rho(n) for gold thin films.