Evidence of ratchet effect in nanowires of a conducting polymer

TL;DR

This study demonstrates the ratchet effect in polypyrrole nanowires, where asymmetric doping profiles induce directional dependence in electrical resistance, influenced by nanowire diameter and temperature.

Contribution

It provides experimental evidence of the ratchet effect in conducting polymer nanowires caused by doping-induced asymmetric potential profiles.

Findings

Resistance asymmetry increases with decreasing nanowire diameter.

Resistance asymmetry increases with temperature.

Localized state extension reduces with doping concentration.

Abstract

Ratchet effect, observed in many systems starting from living organism to artificially designed device, is a manifestation of motion in asymmetric potential. Here we report results of a conductivity study of Polypyrrole nanowires, which have been prepared by a simple method to generate a variation of doping concentration along the length. This variation gives rise to an asymmetric potential profile that hinders the symmetry of the hopping process of charges and hence the value of measured resistance of these nanowires become sensitive to the direction of current flow. The asymmetry in resistance was found to increase with decreasing nanowire diameter and increasing temperature. The observed phenomena could be explained with the assumption that the spatial extension of localized state involved in hopping process reduces as the doping concentration reduces along the length of the nanowires.