# Electrical transport and reflectance studies on polypyrrole - $CF_3SO_3^-$ in the vicinity of metal-insulator transition

Mithra, Madan LM and Cao, Y and Cho, Shinuk and Sutar, Dayanand and Lee, K and Menon, Reghu and Subramanyam, SV (2001) Electrical transport and reflectance studies on polypyrrole - $CF_3SO_3^-$ in the vicinity of metal-insulator transition. In: Synthetic Metals, 119 (1-3). pp. 437-438.

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## Abstract

We discuss the disorder induced metal-insulator transition in polypyrrole doped with $CF_3SO_3^-$ in an attempt to understand the electrical transport in the vicinity of the transition. With the temperature dependence of conductivity and magnetotransport measurements performed over a wide temperature range spanning from 1.5K to 300K, we have been able to separate out various regimes of transport. The temperature dependence of conductivity changes from a $\sigma(T) = \sigma(0) + roT^{1/2} + BT^{P/2}$ behaviour reminiscent of conduction in a disordered metal to a $\sigma(T) \sim T^\beta$ dependence at the critical regime and then to a variable range hopping dependence as the MI transition is traversed. Together with the magnetotransport, it is vident that the electron-electron interaction plays a crucial role in determining the conduction near the transition. The dominant dephasing mechanism that determines the temperature dependence of incipient-localization has been accounted for the inelastic scattering of electrons by phonons. Reflectance in the metallic regime has been studied over a wide spectral range from 0.02eV to 6eV. Spectral features like plasma resonance and high reflectivity in the IR, which are unique to a metal, are seen. Localization-modified Drude model has been found to be adequate in describing the energy dependence of the optical conductivity.

Item Type: Journal Article Copyright of this article belongs to Elsevier. Conductivity;Transport measurements;Metal-insulator phase transitions;Polypyrrole and derivatives Division of Physical & Mathematical Sciences > Physics 29 Mar 2007 19 Sep 2010 04:36 http://eprints.iisc.ernet.in/id/eprint/10369