A NEW CALCULATION OF 1 F NOISE IN DISORDERED-SYSTEMS WITH HOPPING TRANSPORT/

The noise spectrum in hopping conduction systems is known to be closel y related to the conductivity, as shown by scaling relationships betwe en the two. The frequency-dependent conductivity and DC conductivity a m related by scaling formulations as well. Percolation theoretical fra meworks, such as used here, generate automatically relationships betwe en frequency-dependent and DC transport properties. Under application of a DC field, the power spectrum of the (flicker) noise is usually in versely proportional to the frequency, proportional to the square of t he applied held and, in crystalline germanium at low temperature, T, i t has been found to be independent of T. Charge transport is tradition ally represented in terms of a random impedance network in which all p airs of sites are connected by resistors. By considering cluster polar ization effects of large clusters of resistors on the critical, blocki ng resistances on the percolation path, it is shown here that hopping conduction systems at low temperatures should generate a universal fli cker noise proportional to the applied held squared, the inverse of th e frequency, and independent of T. The cluster polarization effects co nsidered arise from charge transported through large numbers of resist ors in sequence, a process which, as it turns out, appears to generate much more visible effects in the noise than in the conductivity.