Superconducting transport characteristics of YBa/sub 2/Cu/sub 3/O/sub 7- delta / grain boundary junctions

The superconducting transport of YBa/sub 2/Cu/sub 3/O/sub 7- delta / grain boundary junctions (GBJs) fabricated by laser ablation deposition on SrTiO/sub 3/ bicrystals is discussed. For narrow GBJs with a width smaller than about four times their Josephson penetration depth, the current-voltage characteristics can be modeled closely by the resistively shunted junction (RSJ) model and the magnetic field dependence of the critical current is Fraunhofer-pattern-like. The temperature dependence of the critical current is proportional to (1-T/T/sub c/)/sup 2/ close to T/sub c/. The characteristic voltages V/sub c/=J/sup gb//sub c/ rho /sub N/, where J/sup gb//sub c/ is the critical current density and rho /sub N/ the normal resistance times unit area of the GBJs, range between 0.2 and 8 mV at 4.2 K and scale proportional to (1/ rho /sub N/)/sup 1.5/. The transport characteristics of the GBJs are in agreement with a SNINS-type junction model.