Persistent photoconductivity on ion irradiated carbon films prepared by plasma assisted chemical vapor deposition and determination of traps in the pseudo-gap region

The defects created by ion beam irradiation in disordered conducting carbon films have been studied by the photoconductivity technique. A very complex distribution of traps created mostly by random displacement of carbon atoms by energetic ion beam from its polymeric matrix showed a persistent photoconductivity at low temperature. The decay time constant estimated from the photocurrent is around 15 s at 10 K. From the time constant and the intensity of photocurrent the density of traps and the corresponding activation energies are calculated. This report shows how slow decay of photocurrent can be applied to probe distribution of traps in the amorphous carbon due to ion bombardment in the most general case. (C) 1996 American Institute of Physics.