PHOTOBLEACHING OF PARAMAGNETIC DEFECTS IN HYDROGENATED AMORPHOUS-CARBON FILMS

We report the light-induced annealing (photobleaching) of thermally in duced paramagnetic defects in hydrogenated amorphous carbon films prep ared by RF-plasma decomposition of methane at RF-power densities of 0. 4 and 0.8 W cm-2. The decrease in the ESR signal due to illumination i s maximum after annealing at 300-degrees-C; moreover, the relative dec rease is larger for the sample prepared at 0.8 W cm-2. We used an expo nential function to model the kinetics for photobleaching. Due to the reversibility of this process we propose the redistribution of optical ly excited charges as the mechanism responsible for photobleaching.