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) has been developed. 200 nm thick c-oriented YBCO films were grown by intermittent thermal coevaporation opt bicrystal yttria-stabilized zirconia substrates. A gold contact overlayer of thickness d(n) was deposited in situ. Normal junction resistances have been measured as a function of d(n) and shunt width w. It was shown that, in accordance with theoretical estimates, the junction shunt resistance is essentially controlled by the c-axis Au/YBCO interface specific resistance and scales as R(s) = 1/w root rho(c) rho(n)/d(n). The product rho(c) rho(n) similar or equal to 3 . 10(-14) Omega(2)cm(3) was estimated from the experimental data, leading to rho(c) approximate to 10(-8) Omega cm(2) for typical values of rho(n) for gold thin films.