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 u nder certain range of self bias values. Log sigma Vs 10(3)/T studies i n 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 cen ters which are changed in the presence of light in a definite way.