  Laser processing has been used to create weakly conducting tracks in
polyimide film. Raman spectroscopy shows that these tracks consist of nanometre
sized graphitic regions contained in a carbon-rich matrix. The measured
temperature dependent and electric field dependent conduction characteristics
show an activated characteristic that is consistent with nearest neighbour
hopping. In addition, discrete percolation pathway switching events are seen
when the system is subjected to significant disturbance from equilibrium.
