Effects of step conditions on the properties of YBCO step-edge Josephson junctions

We have studied transition properties of YBa/sub 2/Cu/sub 3/O/sub 7/ step-edge junctions as a function of the angle of the step-line with respect to the major axes of the SrTiO/sub 3/ substrate. Substrate steps were prepared by Ar ion milling with photoresist mask, and the YBa/sub 2/Cu/sub 3/O/sub 7/ film was deposited by pulsed laser ablation and patterned by ion milling to form junctions. The critical temperature of the junctions was independent of the angle. However, the critical current of the junctions showed a modulation with the angle. A maximum was observed for the step-line oriented parallel to the major axes of the substrate and a minimum for the step-line oriented 45/spl deg/ against the axes. The modulation of the critical current is believed to be caused by the difference in the microscopic structure of the epitaxially grown YBa/sub 2/Cu/sub 3/O/sub 7/ film at the step and also symmetry of the high Tc superconductor.