CONDUCTANCE NOISE IN YBCO THIN-FILMS

Experimental results on the low frequency conductance noise in YBaCuO thin films are presented. The films have been obtained by different fabrication methods (co-evaporation, DC magnetron sputtering and excimer laser deposition). Conductance noise from electron and Cooper-pair number fluctuations, electron mobility fluctuations, percolation and temperature fluctuations have been identified in the different samples. In the temperature range where the sample behaves as a percolating network, the noise is caused by the stochastic switching of weak finks between their normal and superconducting states. This effect dominates in the low temperature part of the superconducting transition in high quality thin films provided temperature fluctuation induced noise is negligible.