The electrical conduction mechanism for the indium tin oxide (ITO)/polypyrrole (PPy)/ITO sandwich type of metal-insulator-metal element was investigated, where electroinactive PPy polymerized in aqueous NaOH solution was used as an insulator. The ITO/PPy/Au element demonstrated a non-linear J-V response exactly the same as that of the ITO/PPy/ITO element, indicating that the carriers do not come from the interface but the bulk of an insulator. For the temperature dependence of the J-V responses of the ITO/PPy/ITO element, Poole-Frenkel emission is confirmed to be a dominant conduction mechanism. The activation energy of PPy electropolymerized for 60 min was calculated to be 0.46 eV on the basis of Poole-Frenkel emission. The activation energy and the conductivity of the PPy film were dependent on polymerization time.
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