Current noise of contacts to YBa2Cu3O7 high T-c superconducting platelets through the transition region

We describe noise measurements in the frequency range 10 Hz-1 MHz on indium contacts to YBCO layers with a LaAlO3 substrate. The spectra are of the 1/ f(alpha) type with alpha = 1.2 above T-c and 1.15 below T-c, Above T-c ther e is burst noise, although the averaged spectra are stable and reproducible . The voltage noise versus temperature, for a fixed current, shows a sharp dip at the transition temperature T-c = 85 K, but is otherwise largely cons tant. The normalized noise S-v/V-2 goes as [R(T)](-2), which is indicative for 1D switching - percolation noise ("p-noise"), predicted previously, but not hitherto observed. This noise is of importance for low-frequency super conducting devices, such as bolometers and pyroelectric detectors, and for microwave devices where mixing with a carrier occurs, Current models of hig h T-c conductance - noise are reviewed and discussed.