Tunnel junctions in a polymer composite

A transparent film of polycarbonate is conducting when it contains long and thin needles of the organic conductor (TSeT)2Cl. Film conductivity of the order of 1 S/cm can be achieved with a content as low as 0.5 vol % of the conducting charge-transfer complex, provided that the needles are obtained by in situ complexation and crystallization during the solution casting of the polymer. We have measured the current/voltage characteristics at different temperatures from 2 to 300 K on both the composite films and on model junctions produced between two needles only. All these data can be understood and fitted to a new three parameter model which is an extension of Sheng’s fluctuation-induced tunnelling idea to arbitrary temperatures and fields.