Dynamic properties and nonequilibrium processes in electron-beam scribed YBa2Cu3O7 Josephson junctions

We present a detailed characterization of the dynamic properties of proximi ty-coupled Josephson junctions in YBa2Cu3O7 fabricated by electron-beam scr ibing. A full description of the low-temperature behavior includes nonequil ibrium processes in the normal barrier as well as wide-junction effects res ulting from the planar geometry. Above similar to 40 K these junctions obey the standard (equilibrium) resistively-shunted junction (RSJ) model in app lied magnetic field.. At lower temperatures, the volt-ampere V(I) curves de velop a temperature-dependent "excess critical current," saturating at 0.5- 0.75 of the total critical current. Below similar to 10 K hysteresis is obs erved. The observed temperature dependence and magnitude of the excess curr ent and hysteresis are qualitatively consistent with published calculations based on the time-dependent Ginzburg-Landau equations. At low temperatures , the V(I) curves in applied field deviate significantly from the RSJ model , which we attribute to wide-junction behavior with a nonuniform bias-curre nt distribution. (C) 1998 American Institute of Physics. [S0003-6951(98)020 35-X].