Nature of the Josephson barrier in electron-beam-written YBa2Cu3O7-delta junctions

We analyze the temperature (T) dependence of the normal-state resistance R-n and critical current I-c in field-emission-gun electron-beam-written YBa2Cu2O7-delta Josephson junctions from the electrode transition temperature (T-c) to 1.5 K. From a theoretical fit to I-c(T) and R-n(T) we find that the Josephson barrier exhibits properties of a small Fermi-surface area, dirty normal metal near its maximum metallic resistivity. Within conventional superconductor-normal-superconductor theory the barrier is 3.5 mean-free-paths long at T-c, with a normal-metal coherence length at T-c intermediate between the clean and dirty limits. [S0163-1829(97)01442-2].