Quality Dependence of Vapor Phase-Polymerized Poly(3,4-ethylenedioxythiophene) Nanofilm on Substrate Pre-Treatment Methods

The quality of a vapor phase-polymerized PEDOT thin film is highly dependent upon a uniform coating of an oxidant such as Fe(III)Cl-3 on a SiO2 surface. The phase states of a coated oxidant solution are deeply affected by the surface character of base substrates, which can be altered via various pre-treatment methods. Therefore, in this study, in order to identify the optimum surface pretreatment method, four different pre-treatment techniques (Ar plasma, O-2 plasma, H2O/Ar plasma, and a SC-1 treatment methods), were carried out on a thermally oxidized Si-wafer surface using a uniform oxidant solution coating. And then, PEDOT films were grown on the oxidant coated surfaces using a vapor phase polymerization method. Those films were further analyzed using several thin film analyzing tools such as a contact angle analyzer, FE-SEM, an optical microscope, FT-IR, and a four point probe. From this analysis, it was discovered that the quality of a PEDOT thin film can be deeply affected by the surface pre-treatment method. In particular, a H2O/Ar plasma-treated SiO2 surface was the most uniformly coated with the oxidant solution, and the PEDOT thin films grown on the SiO2 surface showed a quite low sheet resistance value (543.84 Omega/sq). Such a high quality ultrathin film could be a potential candidate for a transparent flexible electrode for the next-generation of display and/or photovoltaic devices.