Electrical properties of carbon micro coils

Electrical properties of a single piece of carbon micro coil with the diameter of several μm and the length of several mm are studied. The conductivity of the single coil is 30~100 S/cm. The resistance increases step wise by stretching due to disconnection between helices. The temperature dependence of conductivity, which shows a semi-conductive behavior with the apparent activation energy of about 4 meV, indicates the variable range hopping as the transport mechanism.