EDGE JUNCTIONS OF YBA2CU3O7-DELTA NDBA2CU3O7-DELTA/YBA2CU3O7-DELTA THIN-FILM STRUCTURES/

YBa2Cu3O7-delta Josephson junctions in the ramp edge geometry with NdB a2Cu3O7-delta barriers were fabricated by pulsed laser deposition on ( 100) SrTiO3 substrates. The slope of the ramp measured by AFM was simi lar to 20 degrees. The barrier-layer thicknesses were d = 100, 150, 20 0, and 300 Angstrom. The I-V characteristics of the superconductor-nor mal metal-superconductor junctions changed from an RSJ-type to a flux creep like behavior as the temperature decreased. The characteristic d iffraction pattern of the I-c(H) due to the Josephson effect was obser ved, and the Shapiro steps due to the ac Josephson effect were clearly developed under microwave irradiation. The temperature dependence of the critical currents for the YBa2Cu3O7-delta/NdBa2Cu3O7-delta/YBa2Cu3 O7-delta junctions were explained well by de Gennes' proximity theory in the dirty limit. The interface between the superconducting (YBa2Cu3 O7-delta) and the normal (NbBa2Cu3O7-delta) layer turned out to fairly clean, with an interface resistance of similar to 3 x 10(-10) Ohm cm( 2). In the NBCO barrier, the diffusion constant was similar to 3 cm(2) /sec, and the normal coherence length xi(n) was similar to 50 Angstrom near 77 K.