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 x 10(4) 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. (C) 2004 Elsevier B.V. All rights reserved.