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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 13: Polymer Physics IV: Thin Films

CPP 13.1: Vortrag

Dienstag, 27. März 2007, 14:30–14:45, H40

Graphitizing polyimide surfaces — •Irina Lazareva, Yuri Koval, M. Alam, Stefan Strömsdörfer, Slava Dremov, and Paul Müller — Physikalisches Institut III, Universität Erlangen-Nürnberg Erwin-Rommel Str. 1, 91058 Erlangen, Germany

Various polymers can be converted to conducting state by ion irradiation. Recently we demonstrated that irradiation with Ar+ ions of energies even as low as 150 eV is effective. In contrast to high-energy ion bombardment, low-energy ion irradiation transforms only a thin surface layer. Depending on the irradiation conditions, the conducting layer can be partly or completely graphitized. We present our experimental results of graphitization of polyimide by Ar+ ions with energies between 150 eV and 1000 eV. The surface of the irradiated polyimide was investigated by atomic force and scanning tunneling microscopy. The atomic structure of the irradiated polyimide surface confirms the graphitic nature of the conducting layer. Transport properties of the graphitized layers were studied in the temperature range between 4.2 and 300 K. For high resistive films, the conductivity is provided by variable-range hopping. At high electric fields, the conductivity of the graphitized polyimide can be described by a Poole-Frenkel model. At temperatures below 10 K, tunneling becomes the main process of ionization, and a crossover to Fowler-Nordheim emission was observed. For higher radiation fluencies and higher process temperatures, the conductivity increased significantly and we observed semi-metallic behavior.