CONDUCTIVITIES OF POLYSILANES

Measurements of the electrical conductivities of three types of polysi lanes were carried out over a range of de fields and temperatures. The se polymers are varied in substituents and structures with formulas of [C6H5SiCH3](n), [(C6H5SiCH3)(70)(CH3SiH)(30)](n), and [(C6H5SiCH3)(50 ) (C6H5SiH)(30)(CH3Si)(20)](n). Undoped polysilanes behaved as insulat ors since their conductivities were observed in the range of 10(-10) t o 10(-13) S cm(-1), while SbF5-doped polysilanes of all kinds behaved as semiconductors with conductivities in the range of 10(-2) to 10(-4) S cm(-1). No significant difference in conductivities was observed am ong three SbF5-doped polysilanes although these polymers are very diff erent in chemical properties. These experimental results suggest that electrical conductivities of polysilanes are associated with the Si-Si main-chain backbone rather than with the side groups. It is evident t hat the dopant is able to diffuse throughout the bulk of the polymer a nd the conductivity of the doped polymer is a function of the dopant c oncentration from the result of in situ monitoring of the resistance o f the silane homopolymer during SbF5 doping at room temperature. The c onductivities of polysilanes appeared to be temperature-dependent. The activation energy for the conduction of SbF5-doped silane copolymer w as found to change at its glass transition temperature. (C) 1996 John Wiley & Sons, Inc.