RESISTANCE NOISE IN HIGH-TC AND LOW-TC GRANULAR SUPERCONDUCTING FILMS

Measurements of the resistance noise in thick films of Y-Ba-Cu-0, in thick films of Bi-Sr-Ca-Cu-O, and in thin films of NbN, at the superconducting transition are reported. The transition to the R = 0 state was obtained by either changing the temperature at fixed currents or by lowering the current through the sample at fixed temperatures. In both kinds of experiments, we have observed the divergence of the power spectral density S(v)/V2 as the R = 0 state is approached. Our results are consistent with a percolative interpretation of the resistive transition of granular superconductors.