Conductivity Characterization Using Stm Of Polypyrrole Ultrathin Films Prepared From Admicellar Polymerization

Recently admicellar polymerization (AP) has been used to prepare polypyrrole (PPy) ultrathin films of a few nanometers on graphite and mica with success. Surface morphologies of films characterized using atomic force microscopy (AFM) showed interlinked islands of PPy. The electron transport inside such an ultrathin film is believed to take both molecular conduction along the polymer backbones and tunneling conduction between the islands. Conductivity measurement of films formed on insulating mica and conducting indium tin oxide (ITO) glass was performed at controlled humidity using two probes, the needle tip of scanning tunneling microscopy (STM) and a Specially designed "enclosing" electrode. The effects of probe spacing and configuration over thick and thin films on the I-V characteristic were studied. Ring configuration of outer electrode was found to form more conduction paths than gird and tube ones at the same probe spacing. Electroconducting films were compared in conductivity with insulating polystyrene (PS) films, showing the latter were without conductance. A model of power law for measuring PPy film conductivity was proposed.