LOW-FREQUENCY NOISE IN RF-SPUTTERED PB-DOPED 2223 PHASE BISRCACUO THIN-FILMS

Noise measurements were carried out on RF-sputtered Pb-doped 2223 phas e BiSrCaCuO superconducting thin films. No definite relationship betwe en noise and bias current was observed in the superconducting state, h owever, a square-current dependence of noise was found in the normal s tate. The magnitude of the noise in the BiSrCaCuO films at room temper ature was one to five orders of magnitude larger than that in a normal metal. Near the tail of the resistance transition, noise peaks were o bserved that were 3-12 K below the maximum of the derivative resistanc e-temperature curve. Noise dependence on frequency shows an approximat e 1/f relation in both normal and superconducting states. The origin o f the noise in the normal state is believed to be due to thermal fluct uation or resistance fluctuation and the larger noise near zero T(C) i s possibly caused by grain boundaries in the films.