Transport and structural properties of the top and bottom grain boundaries in YBa2Cu3O7-d step-edge Josephson junctions

Filomena Lombardi, Department of Physics, Chalmers University of Technology and Göteborg University , S-41296 Göteborg, Sweden, Sweden, Phone: +46-31-772-3319, Fax: +46-31-772-3471,e-mail:, WWW: On leave from: Physics Department, University of Napoli "Federico II", I-80125 Napoli, Italy

We present a method to separately study the electrical transport properties of the grain boundaries (GBs) formed at the top and at the bottom edges of YBa2Cu3O7-d step-edge Josephson junctions. The step-edge junctions were fabricated on (100) LaAlO3 steps using tilted Ar ion milling to define the electrodes and the microbridges. Due to the shadowing effect of the step, a continuous YBCO stripe remains along and at the bottom of the step on both sides of a microbridge. We found that the top GB is responsible for the weak link behavior of our step-edge junction. The transport properties were correlated with the different microstructural properties of the two GBs formed at the edges of the step.