  We investigated the mechanism for photoconduction in multi-walled carbon
nanotube (MWNT) film of various electrode separations upon near infrared
illumination. In addition to observing strong dependence of photocurrent on the
position of the laser spot, we found that the time constant of the dynamic
photoresponse is slow and increases with increasing electrode separations. The
photoconduction mechanism can be explained by the Schottky barrier modulation
at the metal-nanotube film interface and charge carrier diffusion through
percolating MWNT networks.
