Characterization of metal—oxide—semiconductor field-effect transistor (MOSFET) for polypyrrole and poly (N-alkylpyrrole)s prepared by electrochemical synthesis

In this study, films of the polypyrrole series, polypyrrole (PPy), poly(N-methylpyrrole) (PNMePy) and poly(N-ethylpyrrole) (PNEtPy), are prepared at room temperature by electrochemical polymerization of the corresponding monomer in acetonitrile, utilizing p-toluenesulfonic acid monohydrate (p-TSA) as a supporting electrolyte. The results show that the thermodecomposition temperature, interchain spacing, electrical conductivity and optical absorption peak wavelength decrease with an increase in the alkyl side chain length. On the other hand, the semiconductor characteristics of these conjugated conducting polymers are utilized in the metal—oxide—semiconductor field-effect transistor (MOSFET) fabrication by electrochemical synthesis. The MOSFETs of Au/p-TSA doped PPy (PNMePy, PNEtPy)/SiO2/Si/Au exhibit ideal field-effect characteristics. The channel current, carrier mobility and transconductance of MOSFETs increase dramatically after adequate heat treatment. The carrier mobilities of the PPy and PNEtPy MOSFETs can reach about 1.7 cm2 V−1 s−1, which is close to those of amorphous silicon inorganic transistors (0.1–1.0 cm2 V−1 s−1 used extensively at present.