Non-Ohmic conduction in polydiacetylene thin films

We have studied the current-voltage (I-V) characteristics of polydiacetylene (PDA) thin films in the temperature region 300-1.7 K. It was found that at electric fields higher than 2 × 104 V/cm, the I-V characteristics are strongly super-linear with negative temperature coefficient of starting voltage. Negative gate voltage increases the source-drain current (the effect is more pronounced at low temperature), whereas the magnetic field up to 7 T does not affect it. The results demonstrate that at low temperature the charge transport is mainly supported due to a charge injection and tunneling from the metallic banks, whereas at higher temperatures the activation energy is related to the band gap mismatch between the different polymer chains or granules.