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A simple method of making low-resistivity contacts ( approximately 10-7 Omega cm2) is reported for the first time on Bi-Sr-Ca-Cu-O films. The method basically involves the laying of silver-paste pads on the surface of as-deposited film, their annealing and the subsequent attachment of copper leads. The annealing step thus serves a dual purpose. It not only renders the film superconducting with requisite oxygenation but also helps in the preparation of low-resistivity contacts. The contacts on the film are quite rugged and could withstand several thermal cyclings between 4.2 and 300 K over a period of one month.

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A dc SQUID like geometry with a ring and a pair of constrictions is carved out of bulk Y-Ba-Cu-O superconductor. The I—V curves exhibit hysteresis arising due to trapping of the self fields. The V—Φ curves show multiple flux periodicities with unequal amplitudes. There is twenty fold rise in the amplitude of voltage modulation in cooling from 77 to 4.2 K. The complications of presence of series and parallel arrays of granular junctions are attributed respectively to large and small periodicities observed in V—Φ curves. The modulation structure gets more resolved at 4.2 K due to reduction in thermal noise effects.