The influence of weak localization and coulomb interaction on the low temperature resistance and magnetoresistance of ion implanted metallic polyaniline films

The low temperature conductivity and magnetoresistance of ion implanted (Ar+) metallic polyaniline films have been studied. For the samples with R(1.9K)/R(300K) ~ 1.2, temperature dependence of the sheet resistivity at T < 15 K is described by the law ΔR(T)/R(T0) ~ - 1gT. The temperature coefficient of resistivity for the most metallic samples was found to change sign from negative to positive at T < 20 K and back to negative at T < 1.6 K. Magnetoresistance at T > 1 K was found to be positive and ΔR(H,T)/ΔR(0,T) ~ H2 and ~ lgH in weak and strong magnetic fields. Negative magnetoresistance was observed at T < 1 K in weak perpendicular magnetic fields. The results obtained are explained in terms of weak localization and electron-electron Coulomb interaction theories in a quasi-two-dimensional disordered system.