Electrical conductivity of a single Au/polyaniline microfiber

We report the measurements of conductivity, I-V curve, and magnetoresistance of a single Au/polyaniline microfiber with a core-shell structure, on which a pair of platinum microleads was attached by focused ion beam. The Au/polyaniline microfiber shows a much higher conductivity (∼110S∕cm at 300K) and a much weaker temperature dependence of resistance [R(4K)∕R(300K)=5.1] as compared with those of a single polyaniline microtube [σRT=30–40S∕cm and R(4K)∕R(300K)=16.2]. The power-law dependence of R(T)∝T−β, with β=0.38, indicates that the measured Au/polyaniline microfiber is lying in the critical regime of the metal-insulator transition. In addition, the microfiber shows a H2 dependent positive magnetoresistance at 2, 4, and 6K.