Abstract
The electron localization is increased with increasing one dimensionality of a quasi-one-dimensional disordered system (quasi-1D-DS). This concept is tested by studying the electron localization in the methyl ring-substituted derivative of polyaniline (PAN), poly(o-toluidine) (POT). The studies include the measurements of temperature dependence of the dc conductivity (T), thermoelectric power S(T), microwave conductivity (T), and dielectric constant ε(T) at 6.5 GHz, dc susceptibility χ(T), electron paramagnetic resonance, and electric-field dependence of conductivity σ(F). The experimental results showed greater electron localization in the HCl salt of POT than that of PAN, reflected in much smaller , , and ε, increased Curie susceptibility, and decreased Pauli-like susceptibility. The localization is attributed to the reduced interchain diffusion rate caused by decreased interchain coherence and increased interchain separation, both of which result from the presence of on the rings. The T dependences of lnσ∼- and S(T)∼+B/T are interpreted as quasi-1D variable-range hopping (VRH) between the nearest-neighboring chains. Within the model, σ(F)∼ with scrK∼ can be understood. The charging energy limited tunneling model for granular metals and the three-dimensional VRH model with a Coulomb gap are not consistent with the experiments. Other possible mechanisms for electron localization and the general implications for control of dimensionality and conductivity are discussed.
- Received 20 July 1990
DOI:https://doi.org/10.1103/PhysRevB.43.4373
©1991 American Physical Society