Impedance Properties of Photoelectrochemically and Chemically Prepared Ta/PEDOT Capacitors

抄録

The impedance properties of Ta capacitors fabricated with the conductive polymer poly-3,4-ethylenedioxythiophene (PEDOT), which was polymerized photoelectrochemically (e-PEDOT) or chemically (c-PEDOT) using the oxidizer Fe(III) p-toluenesulfonate, were evaluated. The photoelectrochemically prepared capacitor exhibited higher capacitance than the chemically prepared one, which might be explained by the relative absence of insulating materials near the oxide/e-PEDOT interface compared with the c-PEDOT interface. Moreover, both chemically and photoelectrochemically prepared Ta/PEDOT capacitors have more ideal capacitor characteristics than Ta/liquid electrolyte capacitors do: the real impedance component of both solid-state capacitors is substantially less than that of the Ta/liquid electrolyte capacitors. For c-PEDOT, our data suggest that the real component of the oxide itself was reduced because the Ta anodic oxide film was subjected to heat treatment during chemical polymerization, thereby reducing the real component of the entire Ta/c-PEDOT system. A discrepancy was found in the case of e-PEDOT: the real component of the entire system was smaller, although the real component of the oxide itself was markedly greater during the photoelectrochemical process.