ELECTRICAL-CONDUCTION MECHANISMS IN POLYMER-COPPER-PARTICLE COMPOSITES .2. (1/F)-NOISE MEASUREMENTS IN THE PERCOLATION LIMIT

We have investigated the mechanisms of electrical conduction of polymercopper-particle composites in the low-particle-concentration limit (dilute limit) by electrical-noise measurements. The 1/f flicker noise, observed close to the percolation threshold, has been studied as a function of the current through the sample, frequency (10-2104 Hz), and resistance (101109 ). In this paper we relate the total resistance noise measured on the samples to the local noise due to the different contacts between the particles. The resistance and noise power of the inhomogeneous medium is modeled by an extended effective-medium theory that includes a transition between two different conduction mechanisms near the percolation threshold. This model gives support to our hypothesis that the noise is produced by small electrical contacts between the particles, as well as the node-link picture introduced to characterize the conductive backbone preexisting at the percolation transition in the continuous percolation models. © 1990 The American Physical Society.