METALLIC TRANSPORT-PROPERTIES IN ELECTROCHEMICALLY AS-GROWN AND HEAVILY-DOPED POLYTHIOPHENE AND POLY(3-METHYLTHIOPHENE)

We have studied the temperature dependence of the ordinary 4-terminal conductivity, VSC conductivity, thermoelectric power (TEP) and low-fre quency ESR for ClO4- doped (as-grown) polythiophene (PT) and poly(3-me thylthiophene) (PMeT) as well as for those doped further with HClO4 At high temperatures the VSC conductivity changes with T-2 in the as-gro wn PT, whereas it changes with T-1 in the as-grown PMeT. Such a metall ic behaviour with temperature was also obtained in the low-frequency E SR linewidth. Results of the TEP experiments were suggestive as well o f the metallic characteristics. The low temperature results of both th e VSC and the TEP measurements indicate that a metal-insulator (or sem iconductor) transition takes place at 30K for PT and 10K for PMeT.