2 PARAMETER SCALING OF THE CONDUCTIVITY FOR INSULATING GRANULAR PDXC1-X FILMS

Conductivity measurements are reported for thin (t < 32nm) granular Pd xC1-x films with x < 0.3 on the insulating side of the metal insulator transition (x(p) = 0.3). The granular films consist of small disconne cted metallic Palladium-clusters (PHI almost-equal-to 3nm) embedded in an amorphous Carbon matrix. The temperature dependence of the conduct ivity follows the form sigma(T) = sigma0.exp(-(T0/T)alpha) with alpha = 1/4 at higher temperatures up to T = 300K and alpha = 1/2 at low tem peratures. This is discussed in the framework of electronic hopping tr ansport with and without the influence of a gap in the electronic dens ity of states. The scaling behavior of the conductivity is analysed. U sing both scaling parameters sigma0 and T0 the conductivity data for a ll films with different metal volume fraction x collapse onto one sing le scaling curve.