ON THE ORIGIN OF LOW-FREQUENCY NOISE IN HTCS THIN-FILMS

Pronounced low frequency voltage noise extending into MHz frequencies was observed in current biased granular Y-Ba-Cu-O films. At some particular bias conditions it was possible to isolate the random telegraph voltage noise produced by a single elementary two-level fluctuator. The telegraph signal and the power spectrum of the noise depended strongly on the dc bias current and on the applied magnetic field. On the basis of experimental observations two alternative mechanisms; charge carrier trapping in the barriers of intrinsic Josephson junctions and magnetic flux jumping, auto-detected by intrinsic dc SQUIDS, are proposed as possible sources of the 1/f noise in superconducting high-T(c) films.