Electrically conducting thin films obtained by ion implantation in pyrolyzed polyacrylonitrile

Heat treatment of polyacrylonitrile (PAN) leads to products with semiconduc tor-to-metal range of conductivities. The electrical properties of these ma terials are further modified by ion implantation. The conductivity, 1x10(-7 ) (Omega cm)(-1), Of heat treated PAN at 435 degreesC (PAN435) increases up on ion implantation with As+, Kr+, Cl+ or F+, reaching the maximum value of 8.9x10(-1) (Omega cm)(-1) at a dose of 5x10(16) ion/cm(2) and an energy of 200 KeV for the case of F+ implantation. On the other hand, ion implantati on in the more conducting heat-treated PAN at 750 degreesC (PAN750) leads t o a decrease in the electrical conductivity. It is shown that the conductiv ity modifications are primarily due to structural rearrangements induced by the energetic ions. Specific chemical doping contribution to conductivity is noted for halogen implantation in PAN435. The temperature dependence of conductivity of PAN heat treated at 750 degreesC suggests a two path conduc tion, namely a three dimensional variable range hopping conduction and a me tallic conduction. After ion implantation, the conductivity-temperature dep endence is interpreted in terms of a variable range hopping conduction mech anism.