Optical absorption (15 eV) in rf-deposited hydrogenated (2040 at. %) amorphous diamondlike carbon films has been studied as a function of heat treatment. For E2.5 eV a Tauc behavior is exhibited. Optical band gaps Eg are2.4 eV. At lower energies, band tailing with an Urbach focus is found. E0, the width of the tail, is quantitatively explained in terms of the annealing temperature TH. Increasing TH (<700 K) reduces the hydrogen content, lowers Eg, and appears to harden the films. Eg is determined to be a linear function of E0. Additional analysis was performed in terms of a divergence temperature, T0; the results of this analysis are comparable to those observed in a-Si:H.
ASJC Scopus subject areas
- Condensed Matter Physics