Electrical transport in paratoluene sulfonate doped polypyrrole films at low temperature

Abstract

Transport data for paratoluene sulfonate dope polypyrrole films in the insulating regime and near the metal-insulator (M-I) boundary are presented and analyzed. Samples in the insulating region show a crossover from Mott to Efros–Shklovskii variable range hopping conduction at $\text{T=5\hspace{0.17em}}\mathrm{K}$ and magnetoconductance of these samples is also explained by variable range hopping theory. The power law dependence of conductivity ${\mathrm{\sigma (T)\propto T}}^{\beta }$ is observed for the sample close to metallic side of the M-I transition with β=0.83 for $\text{20\hspace{0.17em}}\mathrm{K}\text{<T<300\hspace{0.17em}}\mathrm{K}$ and β=1/2 for $\text{1.8\hspace{0.17em}}\mathrm{K}\text{⩽T⩽20\hspace{0.17em}}\mathrm{K}.$ The magnetoconductance of this sample is analyzed by three dimensional electron-electron interaction and weak electron localization theory. The inelastic scattering length $L_{\mathrm{in}}$ obeys a power law temperature dependence, $L_{\mathrm{in}}{\mathrm{\propto T}}^{\text{−p/2}}$ with $\text{p=1.}$