Electrically Conducting Thin Films by Ion Implantation of Pyrolyzed Polyacrylonitrile

ABSTRACTHeat treatment of polyacrylonitrile leads to products with semiconductor to metal like conductivities. The electrical properties of these materials are further modified by ion implantation. It is noted that the conductivity (∼10-7 (Ω cm)-1) of heat treated Polyacrylonitrile at 435°C (PAN435) increases upon ion implantation with As+, Kr+, Cl+ of F+ reaching a maximum value of 8.9 × 10-1 (Ω cm)-1 at as does of 5 × 1016 ion/cm2 and an energy of 200 KeV for the case of F+ implantation. On the other hand, ion implantation of the more conducting heat treated PAN at 750°C (PAN750) leads to a decrease in the electrical conductivity of the material. It is proposed that the conductivity 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°C suggests a two path conduction, namely, a three dimensional variable range hopping conduction and a metallic conduction. After ion implantation, the conductivity-temperature dependence is interpreted in terms of a variable range hopping conduction mechanism.