Transport properties of ion-implanted and chemically doped polyaniline films

The low-temperature dc conductivity and magnetoconductivity of ion-implanted (Ar⁺) and chemically doped (H₂{SO}₄) polyaniline films have been studied. The metal-insulator transition has been observed for ion-implanted polyaniline films on increasing the irradiation dose to 3×{10}¹⁷$ ions ${cm}^{{{-}}2}$. The maximum values of the room-temperature conductivity reached 800 S ${cm}^{{{-}}1}$ for ion-implanted and 8 S ${cm}^{{{-}}1}for chemically doped polyaniline films. In both cases, for samples on the insulator side of the metal-insulator transition, σ(T)=σ(0)exp[-({T}₀$/T${)}ᵐ$], where m{~}0.5, whereas for the most heavily ion-implanted polyaniline films {σ}(T){~}T at T>20 K; the minimum in the {σ}(T) occurs at T{~}20 K and a negative magnetoconductance {Δ}{σ}(H,T){~}H² has been observed. It is shown that electron-electron Coulomb interactions play an important role in charge-carrier transport in ion-implanted polyaniline films near the metal-insulator transition. {} 1996 The American Physical Society.