The influence of dopant species on transport properties in as-grown polypyrrole films prepared by electrochemical method

Summary form only given. A transport study was made on electrochemically prepared polypyrrole (PPy) films to elucidate the influence of dopant species on electrical transport properties. We present the experimental results on as-grown PPY films prepared with several kinds of anion species such as Cl0/sub 4-/, PF/sub 6-/, BF/sub 4-/, TsO/sub -/ and HS0/sub 4-/. The conductivities of these as-grown films at room temperature lie between 50 and 200 S/cm depending on the polymerization condition and/or anion species. The temperature dependence of the ordinary 4-terminal resistivity in all PPy´s exhibited semiconductor-like behaviour over the whole temperature range between 1.6-300K, with the only exception of PF/sub 6-/ doped PPy, which showed a turnover to the metal-like dependence below 8K. At 300K, the absolute thermoelectric power S(T) for all the PPy´s takes very small metal-like values(1-10/spl mu/). Characteristic behaviour was observed in their temperature dependence. S(T) is lineady dependent on temperature below about 230K but becomes nearly constant above 230K. The Voltage Shorted-Compaction (VSC) resistivity (pvsc) showed a metallic temperature dependence with its slope definitely changed at 230K, corresponding well to the result of S(T), which implies a transition between metallic states of different nature.