Variation with temperature of the I–V characteristics of polyacetylene nanofibres

The current–voltage (I–V) characteristics of individual nanofibres of doped polyacetylene show a dramatic change from very strong nonlinearities for lightly-doped samples at low temperatures, to nearly ohmic behaviour for higher temperatures and doping levels. At low temperatures (below 10–30 K), the I–V characteristics are independent of temperature and follow the expression for Zener-type tunnelling, as predicted for field-induced tunnelling of the conjugated bond system. At higher temperatures, the I–V characteristics deviate from Zener-type behaviour and the current increases with temperature as thermally-assisted conduction mechanisms become important. The I–V characteristics for the most conductive sample are consistent with our calculations of fluctuation-induced tunnelling.