STEP-EDGE MICROBRIDGES OF YBACUO FILMS DEPOSITED ON CLEAVED MGO SURFACE

We have fabricated and measured step-edge microbridges of on-axis sputter-deposited YBCO films using the steps which exist on the cleaved surface of MgO substrate. The microbridges fabricated over the step behaved as Josephson devices, exhibiting clear Shapiro steps with microwave irradiation at 4.2 K. The critical current of the step-edge microbridge is one to two orders reduced from the critical current of the microbridge that has no steps within the same bridge region. The I(c)R(N) product is 0.5-1 mV with normal resistance of 1-4 OMEGA. The present technique utilizing the cleaved steps of MgO is useful for studying basic characteristics of the weak links with the step-edge structure.