Kr+ ion implanted rigid rod PBO, PBT and ladder BBL polymers show similar transport and optical behavior, with room temperature conductivities increasing from 10-12 S/cm to approximately 102 S/cm after implantation. A metal-insulator transition is observed at Tc to approximately 30 K. Above Tc, the results of a negative magnetoresistance (ΔR/R(H,T)), a weakly temperature dependent conductivity (σ(T)∝Tp, 0.5<p<1), a linearly T-dependent thermopower (S(T)), a Pauli spin susceptibility (χPauli), and a large microwave dielectric constant (εmw) resemble those of disordered metals in which weak localization and e-e interactions dominate the charge transport. Below Tc, the changed behavior of positive ΔR/R, stronger T-dependent σ, and 1/T-dependent S with a continued large and positive εmw all suggest an increased e-e interaction effect which opens up a `Coulomb' gap (approximately 2 meV), likely due to the enhanced localization. The density of states (DOS) is zero only at the center of the gap in accord with the theoretical prediction of the `Coulomb' gap.
|Number of pages||7|
|Issue number||2 -3 pt 6|
|Publication status||Published - 1993 Apr 1|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Materials Chemistry
- Polymers and Plastics