Carrier transport in highly doped polyacetylene

By use of a modified Naarmann's method, we synthesized good quality polyacetylene films. The films were doped highly with iodine and iron chloride. Taking advantage of a scanning electron microscope, we observed contacts between fibres in the sample. At the contact of two fibres, it produced a contact potential barrier between two mutual contact polyacetylene chains of respective fibres and formed a small tunnel junction. Under the thermal activation, electrons of charged solitons in the soliton band can jump into nearby neutral solitons. These jumping electrons can produce thermally activated voltage fluctuations across junctions that impel free electrons to participate in the tunneling conduction. In view of this, the voltage fluctuation probability P(V-T) raised by the thermal fluctuation voltage VT was derived. By use of the fluctuation-induced tunneling conduction theory, and the effective medium theory, the d.c. conductivity formula of the sample was achieved. We measured the temperature dependence of d.c. conductivities of samples and showed that the formula was in good agreement with experimental results. (C) 1997 Elsevier Science Ltd.