Figure 4

Temperature-dependent electrical characterization shows thermally activated charge transport. (A) The conductivity \(\sigma\) of intact filaments and fibre sheaths show a linear relation with the inverted thermal energy \(1/{kT}\), thus following an Arrhenius behaviour with activation energy in the range of 40–50 meV. (B) Independent measurements of the impedance response as a function of temperature confirm this result. The similarity in the semicircle for every temperature implies the thermal activation only to be present in the (bulk) parallel resistance. (C) When fitted to an (RC) circuit, the parallel resistance \({{R}}_{{p}}\) shows a similar thermal activation as found in (A), while the capacitance \({C}_{{p}}\) remained constant as a function of temperature.