Reduction in defect density by annealing in hydrogenated tetrahedral amorphous carbon

Electronic applications of diamond-like carbon have been limited by its relatively high disorder and defect density. We find that the density of paramagnetic defects in hydrogenated tetrahedral amorphous carbon and the Urbach slope of the optical absorption edge can be reduced by annealing at 300 °C, with little effect on the optical gap. This leads to a reduction in the dark conductivity and an increase in the photosensitivity. The effect is attributed to the migration of hydrogen through the C–C network, to allow better passivation of dangling bonds and a modification of the more weakly bonded sp2 clusters with narrower local band gaps.