1/f noise through the metal-nonmetal transition in percolating composites

We have measured the 1/f noise through the metal-nonmetal transition in carbon black/polymer composites as a function of temperature and doping. At the electronic transition, the resistivity power spectrum S-rho varies as S(rho)similar to rho(Q), with Q=2.77, in agreement with classical three-dimensional percolation. At lower temperatures, a crossover to tunneling-dominated transport occurs with S(rho)similar to ln S-rho/rho(2). Our results show that 1/f noise can be a more sensitive technique than resistivity itself for probing transport behavior near a percolation-induced electronic transition. (C) 2000 American Institute of Physics. [S0003-6951(00)02505-5].