Dielectric properties of pyrolysed polyimide films

We have studied the dielectric properties, in the frequency range 10−4–107 Hz, of polyimide films that were heat treated in vacuum in order to increase their conductivity. Films with electrical properties at the threshold between the insulating and conducting states show an anomalous low frequency dispersion composed of two power laws. The experimental results are consistent with electrical conduction in random one-dimensional chains. Also contact effects are present in our spectra. We conclude that the conducting inclusions formed upon heat treatment of polyimide films are arranged in linear chains.