TRANSPORT AND STRUCTURAL-PROPERTIES OF THE TOP AND BOTTOM GRAIN-BOUNDARIES IN YBA2CU3O7-DELTA STEP-EDGE JOSEPHSON-JUNCTIONS

We present a method to study separately the electrical transport prope rties of the grain boundaries (GBs) formed at the top and at the botto m edges of YBa2Cu3O7-delta(YBCO) step-edge Josephson junctions. The st ep-edge junctions were fabricated on (100) LaAlO3 steps using tilted A r ion milling to define the electrodes and the microbridges. Due to th e 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 foun d that the top GB is responsible for the weak link behavior of our ste p-edge junctions. The transport properties were correlated with the di fferent microstructural properties of the two GBs formed at the edges of the step. (C) 1998 American Institute of Physics.