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 σ Vs 103/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 ⋟ 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.