ONSET OF PHOTOCONDUCTION IN HYDROGENATED AMORPHOUS-CARBON FILMS PREPARED BY RF ASYMMETRIC PECVD TECHNIQUE

Hydrogenated amorphous carbon (a-C:H) films grown on glass substrates by asymmetric RF plasma CVD process exhibit onset of photoconduction under certain range of self bias values. Log sigma Vs 10(3)/T studies in these films indicate that twice the activation energy equals optical band gap at high temperature. At intermediate and lower temperatures. the difference of dark and photoactivation energies is congruent-to 0.15 eV. This indicates that the material has well defined trapping centers which are changed in the presence of light in a definite way.