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

We have measured the 1/f noise through the metal-nonmetal transition in car bon black/polymer composites as a function of temperature and doping. At th e electronic transition, the resistivity power spectrum S-rho varies as S(r ho)similar to rho(Q), with Q=2.77, in agreement with classical three-dimens ional percolation. At lower temperatures, a crossover to tunneling-dominate d 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 fo r probing transport behavior near a percolation-induced electronic transiti on. (C) 2000 American Institute of Physics. [S0003-6951(00)02505-5].