(formula presented) or flicker noise in cellular percolation systems

C. Chiteme, D. S. McLachlan, I. Balberg

Research output: Contribution to journalArticlepeer-review

Abstract

Flicker or (formula presented) noise is studied in a series of four composite discs, which consists of carbon black (ground and unground), graphite, and graphite/boron nitride, as the conducting components coating, and a common insulating matrix of talc wax. The measurements were done on the conducting side (formula presented) of the critical volume fraction (formula presented) within a frequency range of (formula presented) The results are analyzed in terms of Hooge’s empirical formula with frequency and voltage exponents (formula presented) and m, respectively. Values of (formula presented) obtained are in the range 0.97–1.2. Samples with larger (formula presented) have (formula presented) while those with smaller (formula presented) have m significantly lower than 2. The normalized noise at 10 Hz (formula presented) obey the well-established relationships (formula presented) and (formula presented) where V is the voltage across the sample with resistance R, while m, k, and w are exponents. However, a change in the value of the exponent k and w was observed in the measured systems, with k taking the values (formula presented) close to (formula presented) and (formula presented) further into the conducting region. Values of (formula presented) range from (formula presented) while (formula presented) The (formula presented) are observed when (formula presented) The nonuniversality of the (formula presented) and (formula presented) regimes are interpreted as due to the superposition of the behavior that results from the geometry (a random voidlike structure) and the behavior resulting from the presence of non-Ohmic, intergranular contacts between the conducting grains. These exponents are tested for consistency using (formula presented) and compared with predictions from recent theoretical models.

Original languageEnglish
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume67
Issue number2
DOIs
StatePublished - 2003

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